Indian Streams Research Journal
Vol 4 Issue 10 Nov 2014
ISSN No : 2230-7850 ORIGINAL ARTICLE
International Multidisciplinary Research Journal
Indian Streams Research Journal
Executive Editor Ashok Yakkaldevi
Editor-in-Chief H.N.Jagtap
Welcome to ISRJ RNI MAHMUL/2011/38595 ISSN No.2230-7850 Indian Streams Research Journal is a multidisciplinary research journal, published monthly in English, Hindi & Marathi Language. All research papers submitted to the journal will be double - blind peer reviewed referred by members of the editorial board.Readers will include investigator in universities, research institutes government and industry with research interest in the general subjects.
International Advisory Board Flávio de São Pedro Filho Federal University of Rondonia, Brazil
Mohammad Hailat Dept. of Mathematical Sciences, University of South Carolina Aiken
Hasan Baktir English Language and Literature Department, Kayseri
Kamani Perera Regional Center For Strategic Studies, Sri Lanka
Abdullah Sabbagh Engineering Studies, Sydney
Ghayoor Abbas Chotana Dept of Chemistry, Lahore University of Management Sciences[PK]
Janaki Sinnasamy Librarian, University of Malaya
Ecaterina Patrascu Spiru Haret University, Bucharest
Romona Mihaila Spiru Haret University, Romania
Loredana Bosca Spiru Haret University, Romania
Delia Serbescu Spiru Haret University, Bucharest, Romania
Fabricio Moraes de Almeida Federal University of Rondonia, Brazil
Anurag Misra DBS College, Kanpur
Anna Maria Constantinovici AL. I. Cuza University, Romania Ilie Pintea, Spiru Haret University, Romania Xiaohua Yang PhD, USA
George - Calin SERITAN Faculty of Philosophy and Socio-Political Sciences Al. I. Cuza University, Iasi
......More
Titus PopPhD, Partium Christian University, Oradea,Romania
Editorial Board Iresh Swami Pratap Vyamktrao Naikwade ASP College Devrukh,Ratnagiri,MS India Ex - VC. Solapur University, Solapur R. R. Patil Head Geology Department Solapur University,Solapur Rama Bhosale Prin. and Jt. Director Higher Education, Panvel Salve R. N. Department of Sociology, Shivaji University,Kolhapur Govind P. Shinde Bharati Vidyapeeth School of Distance Education Center, Navi Mumbai Chakane Sanjay Dnyaneshwar Arts, Science & Commerce College, Indapur, Pune Awadhesh Kumar Shirotriya Secretary,Play India Play,Meerut(U.P.)
N.S. Dhaygude Ex. Prin. Dayanand College, Solapur Narendra Kadu Jt. Director Higher Education, Pune K. M. Bhandarkar Praful Patel College of Education, Gondia Sonal Singh Vikram University, Ujjain
Rajendra Shendge Director, B.C.U.D. Solapur University, Solapur R. R. Yalikar Director Managment Institute, Solapur Umesh Rajderkar Head Humanities & Social Science YCMOU,Nashik S. R. Pandya Head Education Dept. Mumbai University, Mumbai
Alka Darshan Shrivastava G. P. Patankar S. D. M. Degree College, Honavar, Karnataka Shaskiya Snatkottar Mahavidyalaya, Dhar Maj. S. Bakhtiar Choudhary Director,Hyderabad AP India.
Rahul Shriram Sudke Devi Ahilya Vishwavidyalaya, Indore
S.Parvathi Devi Ph.D.-University of Allahabad
S.KANNAN Annamalai University,TN
Sonal Singh, Vikram University, Ujjain
Satish Kumar Kalhotra Maulana Azad National Urdu University
Address:-Ashok Yakkaldevi 258/34, Raviwar Peth, Solapur - 413 005 Maharashtra, India Cell : 9595 359 435, Ph No: 02172372010 Email: [email protected] Website: www.isrj.net
Indian Streams Research Journal ISSN 2230-7850 Impact Factor : 2.1506(UIF) Volume-4 | Issue-10 | Nov-2014 Available online at www.isrj.orgt
REVIEW OF HEAT TRANSFER ENHANCEMENT IN RECTANGULAR CHANNEL SOLID AND BROKEN V-SHAPED RIBS Abdul J. Hakim1 and R. D. Gorle2 1
Student, Mtech Heat Power EngineeringDr. BabasahebAmbedkar College of Engineering Research Nagpur, India 2 Assistant Professor, Mechanical Engineering Department Dr. Babasaheb Ambedkar College of Engineering ResearchNagpur, India Abstract:- Many industries are utilizing thermal systems wherein overheating can damage the system components and lead to failure of the system. The excessive heat so generated must be dissipated to surroundings to avoid such problems for smooth functioning of system. This is especially important in cooling of gas turbine blades, process industries, cooling of evaporators, thermal power plants, air conditioning equipment, radiators of space vehicles and automobiles and modern electronic equipment. In order to overcome this problem, thermal systems with effective emitters such as ribs, fins, baffles etc. are desirable. The need to increase the thermal performance of the systems, thereby affecting energy, material and cost savings has led to development and use of many techniques termed as “Heat transfer Augmentation”. This technique is also termed as “Heat transfer Enhancement” or “Intensification”. Augmentation techniques increase convective heat transfer by reducing the thermal resistance in a heat exchanger. Many heat augmentation techniques has been reviewed, these are surface roughness, plate baffle and wave baffle, perforated baffle, inclined baffle, porous baffle, corrugated channel, twisted tape inserts, discontinuous Crossed Ribs and Grooves. Most of these enhancement techniques are based on the baffle arrangement. Use of Heat transfer enhancement techniques lead to increase in heat transfer coefficient but at the cost of increase in pressure drop.This review paper is based on different types of baffles and their different arrangements. Studies show that there are some economical heat transfer enhancement techniques. Keywords: Enhancement, Baffles heat transfer and turbulent flow.
I.INTRODUCTION (Heading 1)
Heat transfer augmentation techniques (passive, active or a combination of passive and active methods) are commonly used in areas such as process industries, heating and cooling in evaporators, thermal power plants, air-conditioning equipment, refrigerators, radiators for space vehicles, automobiles, etc. Passive techniques, where inserts are used in the flow passage to augment the heat transfer rate, are advantageous compared with active techniques, because the insert manufacturing process is simple and these techniques can be easily employed in an existing heat exchanger. In design of compact heat exchangers, passive techniques of heat transfer augmentation can play an important role if a proper passive insert configuration can be selected according to the Bharat Wandhare1 and R. D. Gorle2 ,“REVIEW OF HEAT TRANSFER ENHANCEMENT IN RECTANGULAR CHANNEL SOLID AND BROKEN V-SHAPED RIBS ” Indian Streams Research Journal | Volume 4 | Issue 10 | Nov 2014 | Online & Print
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. Review Of Heat Transfer Enhancement In Rectangular Channel Solid And Broken V-shaped Ribs heat exchanger working condition (both flow and heat transfer conditions). In the past decade, several studies on the passive techniques of heat transfer augmentation have been reported. The project is a review on progress with the passive augmentation techniques in the recent past and will be useful to designers implementing passive augmentation techniques in heat exchange. Twisted tapes, wire coils, ribs, fins, dimples, etc., are the most commonly used passive heat transfer augmentation tools. In the present paper, emphasis is given to works dealing with twisted tapes and wire coils because, according to recent studies, these are known to be economic heat transfer augmentation tools. Heat exchangers have several industrial and engineering applications. The design procedure of heat exchangers is quite complicated, as it needs exact analysis of heat transfer rate and pressure drop estimations apart from issues such as long-term performance and the economic aspect of the equipment. The major challenge in designing a heat exchanger is Heat exchangers have several industrial and engineering applications. The design procedure of heat exchangers is quite complicated, as it needs exact analysis of heat transfer rate and pressure drop estimations apart from issues such as long-term performance and the economic aspect of the equipment. The major challenge in designing a heat exchanger is to make the equipment compact and achieve a high heat transfer rate using minimum pumping power. Techniques for heat transfer augmentation are relevant to several engineering applications. In recent years, the high cost of energy and material has resulted in an increased effort aimed at producing more efficient heat exchange equipment. Furthermore, sometimes there is a need for miniaturization of a heat exchanger in specific applications, such as space application, through an augmentation of heat transfer. For example, a heat exchanger for an ocean thermal energy conversion (OTEC) plant requires a heat transfer surface area of the order of 10,000 m2/MW. Therefore, an increase in the efficiency of the heat exchanger through an augmentation technique may result in a considerable saving in the material cost. Dong Hyun Lee a, Dong-Ho Rhee b, Kyung Min Kim a, HyungHee Cho a, Hee Koo Moon, “Performed Detailed measurement of heat/mass transfer with continuous and multiple Vshaped ribs in rectangular channel.” They Investigated Effects of aspect ratio on heat/mass transfer were investigated in rectangular channels with two different V-shaped rib configurations, which are continuous V-shaped rib configuration with a 60 attack angle, and multiple (staggered) V-shaped rib configuration with a 45 attack angle. They concluded Effects of aspect ratio on heat/mass transfer were investigated in rectangular channels with two different V-shaped rib configurations, which are continuous V-shaped rib configuration with a 60o attack angle, and multiple (staggered) V-shaped rib configuration with a 45o attack angle. The square ribs were attached on the test section in a parallel manner. A naphthalene sublimation method was used to measure the local heat/mass transfer coefficients. For the continuous V-shaped rib configuration, two pairs of counter-rotating vortices were generated in the channel, and high transfer region was formed at the center of the ribbed walls. However, for the multiple V-shaped rib configuration with 45o attack angle, asymmetric secondary flow patterns were generated due to its geometric features, resulting in uniform heat/mass transfer distributions. The effect of channel aspect ratio was more significant for the continuous 60o V-shaped rib than for the multiple 45o V-shaped rib configuration. A fluid flowchannel is easily found in various energy conversion systems. Enhancing convective heat transfer in a channel can improve the durability of hot components of gas turbine engine, the effectiveness of heat exchanger and the efficiency of solar air heater, etc. Heat transfer can be improved by installing various turbulators such as ribs, dimples and baffles. Introducing ribs to a coolant channel is one of the most typical methods to enhance heat transfer between solid surfaces and fluid flow. The rib turbulators augment heat transfer in the internal cooling passages because they cause flow separation and reattachment, which result in breakage of the laminar sublayer. In addition, when the angled ribs are installed in a channel, the heat transfer is enhanced with generated secondary flow structures. Karwa et al. reported that 10w40% augmented thermal efficiency was obtained by installing ribs on the absorber plates of solar air heaters. Indian Streams Research Journal | Volume 4 | Issue 10 | Nov 2014
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. Review Of Heat Transfer Enhancement In Rectangular Channel Solid And Broken V-shaped Ribs In the last few decades, many studies have been performed to find optimal conditions of various rib design parameters include rib height, angle of attack, rib-to-rib pitch and rib arrangement. Mittal et al. compared the efficiency of various roughness elements and concluded that inclined ribs including V-shaped ribs possessed better efficiency in the higher range of Reynolds number (more than 12,000). In recent years, the V-shaped rib configurations have been widely investigated. Choi et al. measured the detailed heat/mass transfer distribution in a square channel with V- and L-shaped continuous/discrete ribs. The results showed that continuous L-shaped ribs had higher heat transfer rate than the other ribs. However, discrete L-shaped ribs showed better thermal performances due to the low friction loss. Lau et al. investigated the average and local heat transfer characteristics in a square channel with V-shaped rib arrangements. They reported that 60 and 45 V-shaped ribs enhanced heat transfer on both ribbed and smoothwalls, but caused higher pressure drop than angled full ribs. Han et al. studied the V- and L-shaped ribs with a different angle of attack and compared the results with simple angled rib cases of parallel/cross arrangements. The research demonstrated that the 60o ribs had higher heat transfer coefficients with higher friction loss than the 45o ribs for both the V-shaped and angled rib cases. Taslim et al. performed experiments with 13 different rib configurations, including V- and L-shaped ribs, and reported that V- and L-shaped ribs showed highest heat transfer rate. Rib turbulators may also be employed for intermediate turbine ducts between the high pressure turbine (HPT) and low pressure turbine (LPT). An intermediate turbine duct (ITD) in Fig. 1.2a, is often used in modern jet engines to guide the flow from the HPT to LPT. From Fig. 1.2b, ITD is characterized by two complex structures; the hot liner and cold load carrying structure. Since the pressure at HPT is usually higher than LPT, cooling air is usually required to purge cavities between cold and hot structures in order to avoid ingestion of gas path air into the cavities (segmented liner) and to limit the temperature of the cold structure. The cooling air is inserted in order to initiate a swirl flow and to impinge on the outer wall of the cavity. II.HEAT TRANSFER ENHACEMENT A. RIBS To understand the physics of the flow connected to the rib, Fig. 1 provides the schematic of flow as well as the associated local heat transfer in the inter-rib region. A pair of periodic ribs was schematically placed on one principle wall of a channel. The rib height (e) and rib-to-rib spacing (p) are the nomenclature commonly used for the geometrical feature of ribs.
Figure1. Rib Arrangement on the heater plate (Transverse Ribs) In principal, ribs disturb the boundary layer due to flow separation and reattachment. From this figure, the boundary layer separates induced by the upstream rib, forms a separated shear layer, and eventually reattaches on the wall. A reversed flow boundary layer originates at the reattachment point and grows in thickness towards the upstream rib. After reattachment, the flow starts to Indian Streams Research Journal | Volume 4 | Issue 10 | Nov 2014
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. Review Of Heat Transfer Enhancement In Rectangular Channel Solid And Broken V-shaped Ribs redevelop until it approaches the next rib subsequently another separation induced by the downstream rib occurs. This figure also shows the typical local heat transfer distribution in the interrib region for a fully developed channel. A local minimum heat transfer occurred at point X8 due to the recirculation flow. A local maximum occurred at point X9 due to the flow reattachment. A decrease of the local heat transfer after reattachment continued until a minimum value occurred at X10 due to the flow separation. That part of the flow trapped within a small vortex at corner of the downstream rib produces a local maximum of the heat transfer, as shown at X11 [12]. For this reason, the local heat transfer in the separated-reattached flow is larger than those of an un-disturbed boundary layer. However, the heat transfer enhancement in the separated-reattached flow is typically accompanied by an increase in the fluid pressure drop and pumping power. Accordingly, the identification of the rib geometry features is fundamental, to obtain the best heat transfer performance by considering both heat and momentum transfer characteristics [13] III.RIB GEOMETRICAL FEATURES Rib heat transfer performance is significantly dependent on geometrical features and flow conditions. Effects on the flow are characterized by the flow Reynolds number and the rib geometry including rib height (e), rib spacing (p), rib angle-ofattack and rib shape. Based on these, the rib geometrical features are commonly introduced as non-dimensional parameters such as rib pitch-torib height ratio (p/e) and the
Figure 2. Rib Configurations Ribs can be placed relative to the main direction of the flow with a diversity of angles. The ribs with orthogonal angle are called transverse ribs. The angled ribs have angles relative to the
Indian Streams Research Journal | Volume 4 | Issue 10 | Nov 2014
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. Review Of Heat Transfer Enhancement In Rectangular Channel Solid And Broken V-shaped Ribs main flow direction less than 90 degrees. First studies of heat transfer and pressure drop in ribroughened rectangular channels considered continuous, regularly spaced, transverse ribs on two opposite sides (see, e.g., [14-15]). Further studies showed that the use of angled ribs can have a significant impact on local heat transfer and pressure drop because of the secondary flow induced by the inclined rib. Early studies of heat transfer performance in square/rectangular channels with angled ribs drew the guidelines for the appropriate thermal design of a channel with angled rib turbulators. So for instance, in rectangular channels (p/e = 10-20 and e/Dh = 0.047-0.102) with AR larger than 2 (ribbed on the wider sides), it was found that angled ribs have a smaller impact on heat transfer performance, with lower pressure drop compared to transverse ribs. In contrast, the rib angle effect is more important for the small AR (1/2 and 1/4), with similar or slightly higher pressure drop as compared with transverse ribs but significantly higher heat transfer coefficient. In order to promote higher levels of flow turbulence, further experiments were performed by other geometries such as broken ribs [see, e.g., 24, 25], V-shaped ribs discrete V- and W- shaped ribs [see, e.g., 27], but these required more fabrication efforts. Figure 2, summarizes a catalogue of different rib configurations. Numerous experimental studies have been conducted in square or rectangular channels ribbed on two opposite walls, the other walls remaining smooth, with uniform heat flux conditions on all sides. Such a situation is typically encountered in the internal cooling of turbine blades that constitutes the major application of these studies, as outlined in the book by Han et al. [2]. Over the years several publications have addressed the state-of-the-art review of turbine blade cooling and the analysis of heat transfer and friction characteristics in a wide range of such above rib configurations in variously sized cooling channels. The foregoing discussion reminds readers that the experimental studies by far, have been developed in response to demand for improvement of the heat transfer performance in the internal cooling passages in turbine blades. Those studies in the laboratories have been developed to investigate geometrical effects by simulating the internal cooling passages of turbine blades as channels with different aspect ratios. The majority of the experimental studies have been developed for the analysis of heat transfer and friction characteristics in channel with fully developed flow. From the turbine cooling design perspective, it is also important to know the detailed distributions of the local heat transfer for developing flow in short rectangular (L/D = 10-15) channels with rib turbulators. The interest was to find out if the results of the highest heat transfer coefficient with angled ribs (60º and 75º) and the best heat transfer performance (30º and 45º) obtained in a long square duct at fully developed flow hold satisfactory in short rectangular channels with two opposite ribbed walls and yet developing flow. Therefore, investigations to determine the effect of the rib angle-of-attack on the local heat transfer distributions in short rectangular channels of different channel aspect ratios has been performed. For further details, the readers are referred to the book by Han et al. [2]. Based on the reported information, this thesis is focused on continuous transverse rib configuration. Moreover, it is mainly focused on the effect of two important geometrical parameters: the rib height-to-channel hydraulic diameter ratio (e/Dh) and rib pitch-to-rib height ratio (p/e). IV. RIB CONFIGURATION A. Effect of Rib Height • The rib height-to-channel hydraulic diameter ratio (e/Dh), the so-called blockage ratio, is a characteristic of a kind of roughness. Clearly, e/Dh cannot be an effective factor as the rib height is so small that the ribs are all contained within the boundary layer. If the surface-roughness height is of the same order of magnitude as the thickness of the boundary layer, the boundary layer is disturbed due to the complex flow separation and reattachment and thus it enhances the heat transfer. • An increase of the rib height may increase the heat transfer. Accompanied with this, the pressure loss tends to increase with an increase of the rib height. The hysical reason for such a trend is the increase blockage of the flow passage which leads to increases flow retardation. If the core flow is
Indian Streams Research Journal | Volume 4 | Issue 10 | Nov 2014
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. Review Of Heat Transfer Enhancement In Rectangular Channel Solid And Broken V-shaped Ribs strongly disturbed by the presence of a large rib height, it leads to a more sharp increase of the flow retardation than an enhancement of heat transfer [28]. B. Effect of Rib Spacing Although, the periodic rib may be considered as surface-roughness geometry, it may also be considered as a problem in boundary layer separation and reattachment [29]. Figure 1.6 shows a catalogue of flow patterns downstream of a rib, as a function of p/e. The existence of an optimum value of p/e is due to the fact that at small p/e, the flow separates after each rib but does not reattach in the inter-rib region where a single recirculation bubble is formed and heat transfer is thus impaired (i.e., p/e ≤ ５）．
Figure 3.Flow patterns as a function of p/e On the other hand, the effect of the ribs seems to be excessively diluted at large p/e. The physical reason is that the reattachment point at the wall is reached and a boundary layer begins to grow in thickness before the succeeding rib is encountered. Then, the local heat transfer downstream of the reattachment point has a larger distance for continuous decay and hence the heat transfer is reduced. The length of the separation region behind the rib does not change as the pitch increases, while the distance between the reattachment point and the following rib increases with pitch [30]. At the optimum value p/e, the flow does reattach close to the next rib. The optimum value of p/e was found approximately to be 10 for rectangular channels with ribs on two opposite sides (e.g., see [13]). It is then reasonable that more closely spaced ribs yield higher pressure losses. In the light of the optimum p/e ratio, it is of interest in this thesis to review the effect of a wide range of p/e ratios on local heat transfer distribution. However, such information in a wide range is limited to two opposite rib-roughened walls. Then, those research papers will be included as
Indian Streams Research Journal | Volume 4 | Issue 10 | Nov 2014
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. Review Of Heat Transfer Enhancement In Rectangular Channel Solid And Broken V-shaped Ribs a complementary review, but with an effort to provide such effects qualitatively. Cavallero and Tanda [31] investigated the effect of small p/e ratio (i.e., p/e = 4) on local heat transfer distributions in a rectangular channel (AR = 5) where the thermal field was not fully developed. The inter-rib heat transfer distribution was characterized by a monotonic increase that was periodically repeated after 3-4 ribs (see Fig. 1.7). Such a feature of the heat transfer distribution was reported by the presence of a trapped vortex between the ribs without a reattachment point. This led to a weak heat transfer performance in terms of the ratio between the averaged Nu numbers over the ribbed and the smooth channels. Aliaga et al. [12] investigated the effect of p/e = 5 by heat transfer measurement and flow visualization in a rectangular channel (AR = 2.9) including the fully developed as well as the entrance region. The fully developed flow field was established after the third rib (Fig. 1.8a). Accordingly, the periodic fashion of the local heat transfer distribution for the fully developed was reported after the second rib (see Fig. 1.8b). The feature of the heat transfer distribution suggested the presence of a trapped vortex due to the closely spaced ribs without a reattachment point. V. CONCLUSION This review paper concerns about heat transfer enhancement in a rectangular channel with ribsand an obstacle.In this paper, the different types of ribs are studied such as continuous ribs, broken ribs, angular ribs at different angle and ribs with different shape. Also we studied about the effect of shape of ribs, effect of rib height, effect of rib spacing in this review paper. Different inventer’s works about each one have beenreviewed and many methods that assist their augmentation effects have been extracted from the literature. The continuous and broken v-shaped ribs are studied and these types of ribs shows a significant increase in the heat transfer rate. REFERENCES 1] Detailed measurement of heat/mass transfer with continuous and multiple V-shaped ribs in rectangular channel, Dong Hyun Lee a, Dong-Ho Rhee b, Kyung Min Kim a, Hyung Hee Cho a, Hee Koo Moonc, Energy 34 (2009) 1770–1778 2] V. K. Garg. Heat Tranfer Research on Gas Turbine Airfoils at NASA GRC. International Journal of Heat and Fluid Flow, 23: 109-136. 2002. 3] An experimental study of flow boiling in a rectangular channel with offset strip fins; Byongjoo Kim a,*, Byonghu Sohn, International Journal of Heat and Fluid Flow 27 (2006) 514–521 4] Experimental study of thermal behaviors in a rectangular channel with baffle of pores, Chu-Wei Lin, International Communications in Heat and Mass Transfer 33 (2006) 985–992. 5] J. C. Han, S. Datta, and S. Ekkad. Gas Turbine Heat Transfer and Cooling Technology, Taylor and Francis. 2000. 6] J. C. Han. Heat Transfer and Friction Characteristics in Rectangular Channels with Rib Turbulators. ASME Journal of Heat Transfer. 110: 321-328. 1988. 7] D. A. Aliaga, J. P. Lamb, and D. E. Klein. Convection Heat Transfer Distributions over Plates with Square Ribs from Infrared Thermography Measurements. International Journal of Heat and Mass Transfer, 37: 363- 374. 1993. 8] G. Tanda. Effect of Rib Spacing on Heat Transfer and Friction in a Rectangular Channel with 45 Angled Rib Turbulators on one/two Walls. International Journal of Heat and Mass Transfer, 54: 1081-1090. 2011. 9] F. Burggraf. Experimental Heat Transfer and Pressure Drop with Two- Dimensional Turbulence Promoter Applied to Two Opposite Walls of a Square Tube, in: A. E. Bergles, R.L. Webb (Eds.), Augmentation of Convective Heat and Mass Transfer, ASME, New York. 70-79. 1970. 10] J. C., Han, L. R. Glickmann, and W.M. Rohsenow. An Investigation of Heat Transfer and Friction for Rib-roughened Surfaces. International Journal of Heat Mass Transfer, 21: 1143-1156. 1978. 11] J.C. Han, and C. K. Lei. Heat Transfer and Friction in Square Ducts With Two Opposite Ribroughened Walls. ASME Journal of Heat Transfer, 106: 774-781. 1984.
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. Review Of Heat Transfer Enhancement In Rectangular Channel Solid And Broken V-shaped Ribs 12] J. C. Han, J. S. Park, and C.K. Lei. Heat Transfer Enhancement in Channels With Turbulence Promoters, ASME Journal of Eng. for Gas Turbines and Power, 107: 628-635,1985. 13] J. C. Han and J. S. Park. Developing Heat Transfer in Rectangular Channels with Rib Turbulators. International Journal of Heat Mass Transfer, 31: 183-195. 1988. 14] J. C. Han, S. Ou, J. S. Park, and C.K. Lei. Augmented Heat Transfer in Rectangular Channels of Narrow Aspect Ratios With Rib Turbulators, International Journal of Heat Mass Transfer, 32: 16191630. 1989. 15] J. S. Park, J. C. Han, Y. Huang, S. Ou, and R. J. Boyle. Heat Transfer Performance Comparisons of Five Different Rectangular Channels With Parallel Angled Ribs. International Journal of Heat Mass Transfer, 35: 2891-2903. 1992.
Abdul J. Hakim Student, Mtech Heat Power Engineering Dr. BabasahebAmbedkar College of Engineering Research Nagpur, India
Indian Streams Research Journal | Volume 4 | Issue 10 | Nov 2014
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ISSN No : 2230-7850 ORIGINAL ARTICLE
International Multidisciplinary Research Journal
Indian Streams Research Journal
Executive Editor Ashok Yakkaldevi
Editor-in-Chief H.N.Jagtap
Welcome to ISRJ RNI MAHMUL/2011/38595 ISSN No.2230-7850 Indian Streams Research Journal is a multidisciplinary research journal, published monthly in English, Hindi & Marathi Language. All research papers submitted to the journal will be double - blind peer reviewed referred by members of the editorial board.Readers will include investigator in universities, research institutes government and industry with research interest in the general subjects.
International Advisory Board Flávio de São Pedro Filho Federal University of Rondonia, Brazil
Mohammad Hailat Dept. of Mathematical Sciences, University of South Carolina Aiken
Hasan Baktir English Language and Literature Department, Kayseri
Kamani Perera Regional Center For Strategic Studies, Sri Lanka
Abdullah Sabbagh Engineering Studies, Sydney
Ghayoor Abbas Chotana Dept of Chemistry, Lahore University of Management Sciences[PK]
Janaki Sinnasamy Librarian, University of Malaya
Ecaterina Patrascu Spiru Haret University, Bucharest
Romona Mihaila Spiru Haret University, Romania
Loredana Bosca Spiru Haret University, Romania
Delia Serbescu Spiru Haret University, Bucharest, Romania
Fabricio Moraes de Almeida Federal University of Rondonia, Brazil
Anurag Misra DBS College, Kanpur
Anna Maria Constantinovici AL. I. Cuza University, Romania Ilie Pintea, Spiru Haret University, Romania Xiaohua Yang PhD, USA
George - Calin SERITAN Faculty of Philosophy and Socio-Political Sciences Al. I. Cuza University, Iasi
......More
Titus PopPhD, Partium Christian University, Oradea,Romania
Editorial Board Iresh Swami Pratap Vyamktrao Naikwade ASP College Devrukh,Ratnagiri,MS India Ex - VC. Solapur University, Solapur R. R. Patil Head Geology Department Solapur University,Solapur Rama Bhosale Prin. and Jt. Director Higher Education, Panvel Salve R. N. Department of Sociology, Shivaji University,Kolhapur Govind P. Shinde Bharati Vidyapeeth School of Distance Education Center, Navi Mumbai Chakane Sanjay Dnyaneshwar Arts, Science & Commerce College, Indapur, Pune Awadhesh Kumar Shirotriya Secretary,Play India Play,Meerut(U.P.)
N.S. Dhaygude Ex. Prin. Dayanand College, Solapur Narendra Kadu Jt. Director Higher Education, Pune K. M. Bhandarkar Praful Patel College of Education, Gondia Sonal Singh Vikram University, Ujjain
Rajendra Shendge Director, B.C.U.D. Solapur University, Solapur R. R. Yalikar Director Managment Institute, Solapur Umesh Rajderkar Head Humanities & Social Science YCMOU,Nashik S. R. Pandya Head Education Dept. Mumbai University, Mumbai
Alka Darshan Shrivastava G. P. Patankar S. D. M. Degree College, Honavar, Karnataka Shaskiya Snatkottar Mahavidyalaya, Dhar Maj. S. Bakhtiar Choudhary Director,Hyderabad AP India.
Rahul Shriram Sudke Devi Ahilya Vishwavidyalaya, Indore
S.Parvathi Devi Ph.D.-University of Allahabad
S.KANNAN Annamalai University,TN
Sonal Singh, Vikram University, Ujjain
Satish Kumar Kalhotra Maulana Azad National Urdu University
Address:-Ashok Yakkaldevi 258/34, Raviwar Peth, Solapur - 413 005 Maharashtra, India Cell : 9595 359 435, Ph No: 02172372010 Email: [email protected] Website: www.isrj.net
Indian Streams Research Journal ISSN 2230-7850 Impact Factor : 2.1506(UIF) Volume-4 | Issue-10 | Nov-2014 Available online at www.isrj.orgt
REVIEW OF HEAT TRANSFER ENHANCEMENT IN RECTANGULAR CHANNEL SOLID AND BROKEN V-SHAPED RIBS Abdul J. Hakim1 and R. D. Gorle2 1
Student, Mtech Heat Power EngineeringDr. BabasahebAmbedkar College of Engineering Research Nagpur, India 2 Assistant Professor, Mechanical Engineering Department Dr. Babasaheb Ambedkar College of Engineering ResearchNagpur, India Abstract:- Many industries are utilizing thermal systems wherein overheating can damage the system components and lead to failure of the system. The excessive heat so generated must be dissipated to surroundings to avoid such problems for smooth functioning of system. This is especially important in cooling of gas turbine blades, process industries, cooling of evaporators, thermal power plants, air conditioning equipment, radiators of space vehicles and automobiles and modern electronic equipment. In order to overcome this problem, thermal systems with effective emitters such as ribs, fins, baffles etc. are desirable. The need to increase the thermal performance of the systems, thereby affecting energy, material and cost savings has led to development and use of many techniques termed as “Heat transfer Augmentation”. This technique is also termed as “Heat transfer Enhancement” or “Intensification”. Augmentation techniques increase convective heat transfer by reducing the thermal resistance in a heat exchanger. Many heat augmentation techniques has been reviewed, these are surface roughness, plate baffle and wave baffle, perforated baffle, inclined baffle, porous baffle, corrugated channel, twisted tape inserts, discontinuous Crossed Ribs and Grooves. Most of these enhancement techniques are based on the baffle arrangement. Use of Heat transfer enhancement techniques lead to increase in heat transfer coefficient but at the cost of increase in pressure drop.This review paper is based on different types of baffles and their different arrangements. Studies show that there are some economical heat transfer enhancement techniques. Keywords: Enhancement, Baffles heat transfer and turbulent flow.
I.INTRODUCTION (Heading 1)
Heat transfer augmentation techniques (passive, active or a combination of passive and active methods) are commonly used in areas such as process industries, heating and cooling in evaporators, thermal power plants, air-conditioning equipment, refrigerators, radiators for space vehicles, automobiles, etc. Passive techniques, where inserts are used in the flow passage to augment the heat transfer rate, are advantageous compared with active techniques, because the insert manufacturing process is simple and these techniques can be easily employed in an existing heat exchanger. In design of compact heat exchangers, passive techniques of heat transfer augmentation can play an important role if a proper passive insert configuration can be selected according to the Bharat Wandhare1 and R. D. Gorle2 ,“REVIEW OF HEAT TRANSFER ENHANCEMENT IN RECTANGULAR CHANNEL SOLID AND BROKEN V-SHAPED RIBS ” Indian Streams Research Journal | Volume 4 | Issue 10 | Nov 2014 | Online & Print
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. Review Of Heat Transfer Enhancement In Rectangular Channel Solid And Broken V-shaped Ribs heat exchanger working condition (both flow and heat transfer conditions). In the past decade, several studies on the passive techniques of heat transfer augmentation have been reported. The project is a review on progress with the passive augmentation techniques in the recent past and will be useful to designers implementing passive augmentation techniques in heat exchange. Twisted tapes, wire coils, ribs, fins, dimples, etc., are the most commonly used passive heat transfer augmentation tools. In the present paper, emphasis is given to works dealing with twisted tapes and wire coils because, according to recent studies, these are known to be economic heat transfer augmentation tools. Heat exchangers have several industrial and engineering applications. The design procedure of heat exchangers is quite complicated, as it needs exact analysis of heat transfer rate and pressure drop estimations apart from issues such as long-term performance and the economic aspect of the equipment. The major challenge in designing a heat exchanger is Heat exchangers have several industrial and engineering applications. The design procedure of heat exchangers is quite complicated, as it needs exact analysis of heat transfer rate and pressure drop estimations apart from issues such as long-term performance and the economic aspect of the equipment. The major challenge in designing a heat exchanger is to make the equipment compact and achieve a high heat transfer rate using minimum pumping power. Techniques for heat transfer augmentation are relevant to several engineering applications. In recent years, the high cost of energy and material has resulted in an increased effort aimed at producing more efficient heat exchange equipment. Furthermore, sometimes there is a need for miniaturization of a heat exchanger in specific applications, such as space application, through an augmentation of heat transfer. For example, a heat exchanger for an ocean thermal energy conversion (OTEC) plant requires a heat transfer surface area of the order of 10,000 m2/MW. Therefore, an increase in the efficiency of the heat exchanger through an augmentation technique may result in a considerable saving in the material cost. Dong Hyun Lee a, Dong-Ho Rhee b, Kyung Min Kim a, HyungHee Cho a, Hee Koo Moon, “Performed Detailed measurement of heat/mass transfer with continuous and multiple Vshaped ribs in rectangular channel.” They Investigated Effects of aspect ratio on heat/mass transfer were investigated in rectangular channels with two different V-shaped rib configurations, which are continuous V-shaped rib configuration with a 60 attack angle, and multiple (staggered) V-shaped rib configuration with a 45 attack angle. They concluded Effects of aspect ratio on heat/mass transfer were investigated in rectangular channels with two different V-shaped rib configurations, which are continuous V-shaped rib configuration with a 60o attack angle, and multiple (staggered) V-shaped rib configuration with a 45o attack angle. The square ribs were attached on the test section in a parallel manner. A naphthalene sublimation method was used to measure the local heat/mass transfer coefficients. For the continuous V-shaped rib configuration, two pairs of counter-rotating vortices were generated in the channel, and high transfer region was formed at the center of the ribbed walls. However, for the multiple V-shaped rib configuration with 45o attack angle, asymmetric secondary flow patterns were generated due to its geometric features, resulting in uniform heat/mass transfer distributions. The effect of channel aspect ratio was more significant for the continuous 60o V-shaped rib than for the multiple 45o V-shaped rib configuration. A fluid flowchannel is easily found in various energy conversion systems. Enhancing convective heat transfer in a channel can improve the durability of hot components of gas turbine engine, the effectiveness of heat exchanger and the efficiency of solar air heater, etc. Heat transfer can be improved by installing various turbulators such as ribs, dimples and baffles. Introducing ribs to a coolant channel is one of the most typical methods to enhance heat transfer between solid surfaces and fluid flow. The rib turbulators augment heat transfer in the internal cooling passages because they cause flow separation and reattachment, which result in breakage of the laminar sublayer. In addition, when the angled ribs are installed in a channel, the heat transfer is enhanced with generated secondary flow structures. Karwa et al. reported that 10w40% augmented thermal efficiency was obtained by installing ribs on the absorber plates of solar air heaters. Indian Streams Research Journal | Volume 4 | Issue 10 | Nov 2014
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. Review Of Heat Transfer Enhancement In Rectangular Channel Solid And Broken V-shaped Ribs In the last few decades, many studies have been performed to find optimal conditions of various rib design parameters include rib height, angle of attack, rib-to-rib pitch and rib arrangement. Mittal et al. compared the efficiency of various roughness elements and concluded that inclined ribs including V-shaped ribs possessed better efficiency in the higher range of Reynolds number (more than 12,000). In recent years, the V-shaped rib configurations have been widely investigated. Choi et al. measured the detailed heat/mass transfer distribution in a square channel with V- and L-shaped continuous/discrete ribs. The results showed that continuous L-shaped ribs had higher heat transfer rate than the other ribs. However, discrete L-shaped ribs showed better thermal performances due to the low friction loss. Lau et al. investigated the average and local heat transfer characteristics in a square channel with V-shaped rib arrangements. They reported that 60 and 45 V-shaped ribs enhanced heat transfer on both ribbed and smoothwalls, but caused higher pressure drop than angled full ribs. Han et al. studied the V- and L-shaped ribs with a different angle of attack and compared the results with simple angled rib cases of parallel/cross arrangements. The research demonstrated that the 60o ribs had higher heat transfer coefficients with higher friction loss than the 45o ribs for both the V-shaped and angled rib cases. Taslim et al. performed experiments with 13 different rib configurations, including V- and L-shaped ribs, and reported that V- and L-shaped ribs showed highest heat transfer rate. Rib turbulators may also be employed for intermediate turbine ducts between the high pressure turbine (HPT) and low pressure turbine (LPT). An intermediate turbine duct (ITD) in Fig. 1.2a, is often used in modern jet engines to guide the flow from the HPT to LPT. From Fig. 1.2b, ITD is characterized by two complex structures; the hot liner and cold load carrying structure. Since the pressure at HPT is usually higher than LPT, cooling air is usually required to purge cavities between cold and hot structures in order to avoid ingestion of gas path air into the cavities (segmented liner) and to limit the temperature of the cold structure. The cooling air is inserted in order to initiate a swirl flow and to impinge on the outer wall of the cavity. II.HEAT TRANSFER ENHACEMENT A. RIBS To understand the physics of the flow connected to the rib, Fig. 1 provides the schematic of flow as well as the associated local heat transfer in the inter-rib region. A pair of periodic ribs was schematically placed on one principle wall of a channel. The rib height (e) and rib-to-rib spacing (p) are the nomenclature commonly used for the geometrical feature of ribs.
Figure1. Rib Arrangement on the heater plate (Transverse Ribs) In principal, ribs disturb the boundary layer due to flow separation and reattachment. From this figure, the boundary layer separates induced by the upstream rib, forms a separated shear layer, and eventually reattaches on the wall. A reversed flow boundary layer originates at the reattachment point and grows in thickness towards the upstream rib. After reattachment, the flow starts to Indian Streams Research Journal | Volume 4 | Issue 10 | Nov 2014
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. Review Of Heat Transfer Enhancement In Rectangular Channel Solid And Broken V-shaped Ribs redevelop until it approaches the next rib subsequently another separation induced by the downstream rib occurs. This figure also shows the typical local heat transfer distribution in the interrib region for a fully developed channel. A local minimum heat transfer occurred at point X8 due to the recirculation flow. A local maximum occurred at point X9 due to the flow reattachment. A decrease of the local heat transfer after reattachment continued until a minimum value occurred at X10 due to the flow separation. That part of the flow trapped within a small vortex at corner of the downstream rib produces a local maximum of the heat transfer, as shown at X11 [12]. For this reason, the local heat transfer in the separated-reattached flow is larger than those of an un-disturbed boundary layer. However, the heat transfer enhancement in the separated-reattached flow is typically accompanied by an increase in the fluid pressure drop and pumping power. Accordingly, the identification of the rib geometry features is fundamental, to obtain the best heat transfer performance by considering both heat and momentum transfer characteristics [13] III.RIB GEOMETRICAL FEATURES Rib heat transfer performance is significantly dependent on geometrical features and flow conditions. Effects on the flow are characterized by the flow Reynolds number and the rib geometry including rib height (e), rib spacing (p), rib angle-ofattack and rib shape. Based on these, the rib geometrical features are commonly introduced as non-dimensional parameters such as rib pitch-torib height ratio (p/e) and the
Figure 2. Rib Configurations Ribs can be placed relative to the main direction of the flow with a diversity of angles. The ribs with orthogonal angle are called transverse ribs. The angled ribs have angles relative to the
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. Review Of Heat Transfer Enhancement In Rectangular Channel Solid And Broken V-shaped Ribs main flow direction less than 90 degrees. First studies of heat transfer and pressure drop in ribroughened rectangular channels considered continuous, regularly spaced, transverse ribs on two opposite sides (see, e.g., [14-15]). Further studies showed that the use of angled ribs can have a significant impact on local heat transfer and pressure drop because of the secondary flow induced by the inclined rib. Early studies of heat transfer performance in square/rectangular channels with angled ribs drew the guidelines for the appropriate thermal design of a channel with angled rib turbulators. So for instance, in rectangular channels (p/e = 10-20 and e/Dh = 0.047-0.102) with AR larger than 2 (ribbed on the wider sides), it was found that angled ribs have a smaller impact on heat transfer performance, with lower pressure drop compared to transverse ribs. In contrast, the rib angle effect is more important for the small AR (1/2 and 1/4), with similar or slightly higher pressure drop as compared with transverse ribs but significantly higher heat transfer coefficient. In order to promote higher levels of flow turbulence, further experiments were performed by other geometries such as broken ribs [see, e.g., 24, 25], V-shaped ribs discrete V- and W- shaped ribs [see, e.g., 27], but these required more fabrication efforts. Figure 2, summarizes a catalogue of different rib configurations. Numerous experimental studies have been conducted in square or rectangular channels ribbed on two opposite walls, the other walls remaining smooth, with uniform heat flux conditions on all sides. Such a situation is typically encountered in the internal cooling of turbine blades that constitutes the major application of these studies, as outlined in the book by Han et al. [2]. Over the years several publications have addressed the state-of-the-art review of turbine blade cooling and the analysis of heat transfer and friction characteristics in a wide range of such above rib configurations in variously sized cooling channels. The foregoing discussion reminds readers that the experimental studies by far, have been developed in response to demand for improvement of the heat transfer performance in the internal cooling passages in turbine blades. Those studies in the laboratories have been developed to investigate geometrical effects by simulating the internal cooling passages of turbine blades as channels with different aspect ratios. The majority of the experimental studies have been developed for the analysis of heat transfer and friction characteristics in channel with fully developed flow. From the turbine cooling design perspective, it is also important to know the detailed distributions of the local heat transfer for developing flow in short rectangular (L/D = 10-15) channels with rib turbulators. The interest was to find out if the results of the highest heat transfer coefficient with angled ribs (60º and 75º) and the best heat transfer performance (30º and 45º) obtained in a long square duct at fully developed flow hold satisfactory in short rectangular channels with two opposite ribbed walls and yet developing flow. Therefore, investigations to determine the effect of the rib angle-of-attack on the local heat transfer distributions in short rectangular channels of different channel aspect ratios has been performed. For further details, the readers are referred to the book by Han et al. [2]. Based on the reported information, this thesis is focused on continuous transverse rib configuration. Moreover, it is mainly focused on the effect of two important geometrical parameters: the rib height-to-channel hydraulic diameter ratio (e/Dh) and rib pitch-to-rib height ratio (p/e). IV. RIB CONFIGURATION A. Effect of Rib Height • The rib height-to-channel hydraulic diameter ratio (e/Dh), the so-called blockage ratio, is a characteristic of a kind of roughness. Clearly, e/Dh cannot be an effective factor as the rib height is so small that the ribs are all contained within the boundary layer. If the surface-roughness height is of the same order of magnitude as the thickness of the boundary layer, the boundary layer is disturbed due to the complex flow separation and reattachment and thus it enhances the heat transfer. • An increase of the rib height may increase the heat transfer. Accompanied with this, the pressure loss tends to increase with an increase of the rib height. The hysical reason for such a trend is the increase blockage of the flow passage which leads to increases flow retardation. If the core flow is
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. Review Of Heat Transfer Enhancement In Rectangular Channel Solid And Broken V-shaped Ribs strongly disturbed by the presence of a large rib height, it leads to a more sharp increase of the flow retardation than an enhancement of heat transfer [28]. B. Effect of Rib Spacing Although, the periodic rib may be considered as surface-roughness geometry, it may also be considered as a problem in boundary layer separation and reattachment [29]. Figure 1.6 shows a catalogue of flow patterns downstream of a rib, as a function of p/e. The existence of an optimum value of p/e is due to the fact that at small p/e, the flow separates after each rib but does not reattach in the inter-rib region where a single recirculation bubble is formed and heat transfer is thus impaired (i.e., p/e ≤ ５）．
Figure 3.Flow patterns as a function of p/e On the other hand, the effect of the ribs seems to be excessively diluted at large p/e. The physical reason is that the reattachment point at the wall is reached and a boundary layer begins to grow in thickness before the succeeding rib is encountered. Then, the local heat transfer downstream of the reattachment point has a larger distance for continuous decay and hence the heat transfer is reduced. The length of the separation region behind the rib does not change as the pitch increases, while the distance between the reattachment point and the following rib increases with pitch [30]. At the optimum value p/e, the flow does reattach close to the next rib. The optimum value of p/e was found approximately to be 10 for rectangular channels with ribs on two opposite sides (e.g., see [13]). It is then reasonable that more closely spaced ribs yield higher pressure losses. In the light of the optimum p/e ratio, it is of interest in this thesis to review the effect of a wide range of p/e ratios on local heat transfer distribution. However, such information in a wide range is limited to two opposite rib-roughened walls. Then, those research papers will be included as
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. Review Of Heat Transfer Enhancement In Rectangular Channel Solid And Broken V-shaped Ribs a complementary review, but with an effort to provide such effects qualitatively. Cavallero and Tanda [31] investigated the effect of small p/e ratio (i.e., p/e = 4) on local heat transfer distributions in a rectangular channel (AR = 5) where the thermal field was not fully developed. The inter-rib heat transfer distribution was characterized by a monotonic increase that was periodically repeated after 3-4 ribs (see Fig. 1.7). Such a feature of the heat transfer distribution was reported by the presence of a trapped vortex between the ribs without a reattachment point. This led to a weak heat transfer performance in terms of the ratio between the averaged Nu numbers over the ribbed and the smooth channels. Aliaga et al. [12] investigated the effect of p/e = 5 by heat transfer measurement and flow visualization in a rectangular channel (AR = 2.9) including the fully developed as well as the entrance region. The fully developed flow field was established after the third rib (Fig. 1.8a). Accordingly, the periodic fashion of the local heat transfer distribution for the fully developed was reported after the second rib (see Fig. 1.8b). The feature of the heat transfer distribution suggested the presence of a trapped vortex due to the closely spaced ribs without a reattachment point. V. CONCLUSION This review paper concerns about heat transfer enhancement in a rectangular channel with ribsand an obstacle.In this paper, the different types of ribs are studied such as continuous ribs, broken ribs, angular ribs at different angle and ribs with different shape. Also we studied about the effect of shape of ribs, effect of rib height, effect of rib spacing in this review paper. Different inventer’s works about each one have beenreviewed and many methods that assist their augmentation effects have been extracted from the literature. The continuous and broken v-shaped ribs are studied and these types of ribs shows a significant increase in the heat transfer rate. REFERENCES 1] Detailed measurement of heat/mass transfer with continuous and multiple V-shaped ribs in rectangular channel, Dong Hyun Lee a, Dong-Ho Rhee b, Kyung Min Kim a, Hyung Hee Cho a, Hee Koo Moonc, Energy 34 (2009) 1770–1778 2] V. K. Garg. Heat Tranfer Research on Gas Turbine Airfoils at NASA GRC. International Journal of Heat and Fluid Flow, 23: 109-136. 2002. 3] An experimental study of flow boiling in a rectangular channel with offset strip fins; Byongjoo Kim a,*, Byonghu Sohn, International Journal of Heat and Fluid Flow 27 (2006) 514–521 4] Experimental study of thermal behaviors in a rectangular channel with baffle of pores, Chu-Wei Lin, International Communications in Heat and Mass Transfer 33 (2006) 985–992. 5] J. C. Han, S. Datta, and S. Ekkad. Gas Turbine Heat Transfer and Cooling Technology, Taylor and Francis. 2000. 6] J. C. Han. Heat Transfer and Friction Characteristics in Rectangular Channels with Rib Turbulators. ASME Journal of Heat Transfer. 110: 321-328. 1988. 7] D. A. Aliaga, J. P. Lamb, and D. E. Klein. Convection Heat Transfer Distributions over Plates with Square Ribs from Infrared Thermography Measurements. International Journal of Heat and Mass Transfer, 37: 363- 374. 1993. 8] G. Tanda. Effect of Rib Spacing on Heat Transfer and Friction in a Rectangular Channel with 45 Angled Rib Turbulators on one/two Walls. International Journal of Heat and Mass Transfer, 54: 1081-1090. 2011. 9] F. Burggraf. Experimental Heat Transfer and Pressure Drop with Two- Dimensional Turbulence Promoter Applied to Two Opposite Walls of a Square Tube, in: A. E. Bergles, R.L. Webb (Eds.), Augmentation of Convective Heat and Mass Transfer, ASME, New York. 70-79. 1970. 10] J. C., Han, L. R. Glickmann, and W.M. Rohsenow. An Investigation of Heat Transfer and Friction for Rib-roughened Surfaces. International Journal of Heat Mass Transfer, 21: 1143-1156. 1978. 11] J.C. Han, and C. K. Lei. Heat Transfer and Friction in Square Ducts With Two Opposite Ribroughened Walls. ASME Journal of Heat Transfer, 106: 774-781. 1984.
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. Review Of Heat Transfer Enhancement In Rectangular Channel Solid And Broken V-shaped Ribs 12] J. C. Han, J. S. Park, and C.K. Lei. Heat Transfer Enhancement in Channels With Turbulence Promoters, ASME Journal of Eng. for Gas Turbines and Power, 107: 628-635,1985. 13] J. C. Han and J. S. Park. Developing Heat Transfer in Rectangular Channels with Rib Turbulators. International Journal of Heat Mass Transfer, 31: 183-195. 1988. 14] J. C. Han, S. Ou, J. S. Park, and C.K. Lei. Augmented Heat Transfer in Rectangular Channels of Narrow Aspect Ratios With Rib Turbulators, International Journal of Heat Mass Transfer, 32: 16191630. 1989. 15] J. S. Park, J. C. Han, Y. Huang, S. Ou, and R. J. Boyle. Heat Transfer Performance Comparisons of Five Different Rectangular Channels With Parallel Angled Ribs. International Journal of Heat Mass Transfer, 35: 2891-2903. 1992.
Abdul J. Hakim Student, Mtech Heat Power Engineering Dr. BabasahebAmbedkar College of Engineering Research Nagpur, India
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