Performance Analysis of Hemispherical Fin Plate Heat Exchanger

Transcription

1 IJRMET Vo l. 7, Is s u e 2, Ma y - Oc t 2017 ISSN : (Online) ISSN : (Print) Performance Analysis of Hemispherical Fin Plate Heat Exchanger 1 A.Anish, 2 B.Anush Raj, 3 T.Rajesh Thirumalai 1,2,3 Dept. of Mechanical Engineering, Ponjesly College of Engineering Nagercoil, Kanyakumari, India Abstract In this paper the hemispherical fin plate heat exchanger is compared with flat plate heat exchanger theoretically. The hemispherical fin plate is fabricated and tested experimentally and compared with theoretical data calculated. In this experiment fluid to fluid heat transfer processes is followed. Water is used as the working fluid for both hot and cold fluid. The heat transfer and overall heat transfer coefficient characteristics are theoretically and experimentally determined. The mass flow rates are varied and data are collected. Two conditions are followed to calculate the heat transfer and overall heat transfer coefficient firstly the mass flow rate of hot water is kept constant and cold water mass flow rate is varied and secondly the mass flow rate of hot water is varied and mass flow rate of cold water is kept constant. The result from the theoretical calculation show that the hemispherical fin plate heat exchanger has a better heat transfer and overall heat transfer coefficient compared to flat plate heat exchanger.the experimental result for hemispherical fin plate heat exchanger show that the effectiveness of the heat exchanger decreases with increase in heat transfer when two conditions are applied experimentally. The results obtained from experimental data are compared with theoretical data calculated and the results show a good agreement. Keywords Heat Transfer, Overall Heat Transfer Coefficient, Plate Heat Exchanger,Hemispherical Fin Heat Exchanger. I. Introduction Plate fin heat exchangers are widely used in many applications such as food processing, heating or cooling in industrial processes,and in fields including the Natural gas liquefaction, nuclear engineering, offshore processing aerospace industry for its compact size and lightweight properties, as well as in cryogenics where its ability to facilitate heat transfer with small temperature differences is utilized. The plate heat exchanger has more effectiveness, flexibility, compactness and competitive cost when compared with other types of heat exchangers. It is often categorized as a compact heat exchanger to emphasis its relatively high heat transfer surface area to volume ratio. In a plate-fin heat exchanger, the fins can easily be rearranged. Flows like parallel flow, counter flow, and cross flow are possible for different applications if the fins are designed well, the plate-fin heat exchanger works perfectly in flow condition in a counter cross arrangement [1-3]. José Fernández-Seara [4] et al., investigated on the pressure drop and heat transfer characteristics of a titanium brazed plate-fin heat exchanger with offset strip fins. Vaisi [14] et al., carried out an experimental investigation of geometry effects on the performance of a compact louvered heat exchanger. Mao-Yu Wena [5] et al., showed the study of use of the compounded fin constructed for heat exchanger. M. Khoshvaght-Aliabadi [6] et al., carried out a comparison study on seven common configurations of channels used in plate-fin heat exchangers. Yonghan Kim [7] et al., experimental investigated on heat transfer rate of flat plate finned-tube heat exchangers with large fin pitch. Praveen Pandey[8] at el., carried an experimental investigation on the effect of fin pitch on the performance of plate type fins the experiment was conducted for different pitch settings. Hao Peng [9] et al., carried out experimental investigation with five different set arrays of offset fins. Anjun jiao [10] et al., carried out a experimental analysis on Effects of distributor configuration on flow maldistribution in plate-fin heat exchangers. Masoud Asadi [11] et al., investigated on the effects of mass flow rate in terms of pressure drop and heat transfer characteristics. Junqi Dong [12] et al., investigated an experimental studies on the air side heat transfer and pressure drop characteristics for 20 types of multilouvered fin and flat tube heat exchangers. Hui Han [13] et al., analysed A numerical study on compact enhanced fin-and-tube heat exchangers with oval and circular tube configurations. Ya- Ling He [14] et al., conducted a numerically analysis on increase in heat transfer and pressure drop for fin-and-tube heat exchangers with rectangular vortex generators. Chan Hyeok Jeong [15] et al., developed a new shape of plate fin heat exchanger by applying ceases and holes on the plate fin. II. Methodology The fig. 1 shows the schematic diagram of the experimental setup. The system consist of a heater, two over head tanks, valves, two outlet tanks, pipes and Temperature sensing devices. Fig. 1: Schematic Diagram of Experimental Setup A. Design of Heat Exchanger The flow chart in the fig. 2 shows the process carried out in designing the heat exchanger. The heat exchanger is selected according to application required. For the present experiment a plate heat exchanger is considered. Here both the hot and cold fluid used is water. The temperature of the cold water is equal to ambient and hot water temperature is heated to o C. The material used for fabrication of the heat exchanger is stainless steel and aluminium. For high temperature application ceramic materials are used. For the present experiment copper material is used. The heat exchanger dimensions are determined according to the type of application it is going to be used. As the dimension is used to calculate the area of the heat exchanger and the heat transfer depends on the area of the heat exchanger and is also used to calculate the overall heat transfer coefficient. w w w.i j r m e t.c o m International Journal of Research in Mechanical Engineering & Technology 9

2 ISSN : (Online) ISSN : (Print) IJRMET Vol. 7, Issue 2, May - Oct 2017 Selection of the heat exchanger Selection of hot and cold fluid Selection of the material of the heat exchanger Fig. 3: 2D-view of Hemispherical Fin Plate with Baffle Arrangement Dimensions of the heat exchanger Area of the heat exchanger Calculation of the heat transfer and outlet temperatures of the heat exchanger using the design formulas Fig. 2: Design Flow Chart Here a prototype modal of the hemispherical fin plate heat exchanger is fabricated and tested. The dimensions of the heat exchanger are given in Table 1 below. Fig. 4: Image of the Plate With Hemispherical Fins on One Side Table 1: Characteristic Dimensions of the Hemispherical Fin Plate Heat Exchanger Prototype Description Dimensions Length of the plate 360 mm Breadth of the plate 250 mm Thickness of the plate 1 mm number of fins 176 nos Diameter of the fins 10 mm Depth of the fins 4 mm Number of baffles 12 nos Length of the baffles 190 mm Width of the baffles 8 mm The area of the flat plate heat exchanger and hemispherical fin plate heat exchanger are given in Table 2 below. Table 2: Area of the Heat Exchanger Area of the flat plate heat exchanger Area of the Hemispherical fin plate heat exchanger m m2 International Journal of Research in Mechanical Engineering & Technology Fig. 5: Image of the Plate With Hemispherical Fins on Both Sides w w w. i j r m e t. c o m

3 ISSN : (Online) ISSN : (Print) IJRMET Vo l. 7, Is s u e 2, Ma y - Oc t 2017 B. Theoretical Evaluation The following steps are used for the theoretical evaluation The energy balance equation states that the heat released by the hot fluid is equal to heat gained by the cold fluid. The equation is given by, Q = m h cp h (T 1 T 2 ) = m c cp c (t 2 t 1 ) (1) The Number of Transfer Units (NTU) Method is used to calculate the rate of heattransfer in exchangers especially counter flow exchangers when there is insufficient information. The NTU Method is given by, NTU = U x A / Cmin (2) The overall heat transfer coefficient for a heat exchanger is given by 1/U=1/η h h h A h + t/k + 1/η c h c A c (3) The hydraulic diameter, D H, is a commonly used term when handling flow in noncircular tubes and channels. For a rectangular duct, if completely filled with fluid is given by, D h (4) Reynolds number can be defined for a number of different situations where a fluid is in relative motion to a surface. Reynolds number is given by, Re = (5) In heat transfer at a boundary surface within a fluid, the Nusselt number (Nu)is the ratio of convective to conductive heat transfer across normal to the boundary. It is given by, Nu = x (Re) 0.5 / (Pr) (6) The heat transfer coefficient is given by, h = (7) The effectiveness is given by, ε = (8) The fin efficiency is given by η f = k P h A C The Overall fin efficiency is given by (9) η o = 1 (1- η f ) (10) The Velocity Gradient is given by G max = m/a ffh (11) The heat transfer Q is given by. Fig. 6: Experimental Setup C. Experimental Procedure The following procedures are followed for the experimental evaluation the water on the hot side entering the heat exchanger is heated to a temperature of o C by means of an immersion heater. The water at the cold side entering the heat exchanger at ambient temperature o C. The valves of the cold and hot tank are opened and the valves are adjusted to control the flow rate of the fluids entering the heat exchanger. The mass flow rate is calculated by collecting the water in a beaker through the provision provided till 250 ml and the time is noted in sec and thus by dividing the two we get the mass flow rate of both the fluid. The temperatures are measured by using temperature sensors present at the inlet and outlet of cold and hot fluid. The valves are used to control the flow. The flow rate of hot fluid is kept constant and cold fluid flow rate is varied for first set of readings. The temperature readings are noted from the temperature sensors for the above condition. Then the flow rate of cold fluid is kept constant and hot fluid flow rate is varied for second set of readings. The temperature readings are noted from the temperature sensors for the above condition. The temperature readings and tabulated and the following procedure below is used to carry out the experimental Evaluation D. Experimental Evaluation The Mass flow Rate is given by m = (13) The Total Heat transfer by hot fluid is given by Q h = m h cp h (T 1 T 2 ) (14) The Total Heat gained by cold fluid is given by Q c = m c cp c (t 2 t 1 ) (15) Q = ε C min (T 1 t 1 ) (12) w w w.i j r m e t.c o m International Journal of Research in Mechanical Engineering & Technology 11

4 IJRMET Vo l. 7, Is s u e 2, Ma y - Oc t 2017 ISSN : (Online) ISSN : (Print) The Actual Heat Transfer Rate is given by Q act = (16) The Logathmic Mean Temperature Difference is given by ΔTm = (17) The above Fig. 8 shows the comparsion between plate heat exchanger and hemispherical fin plate heat exchanger when hot fluid mass flow rate is varied the graph shows a increase in heat transfer as the mass flow rate increases in both cases but the heat tranfer in case of hemispherical fin plate heat exchanger is higher compared to plate heat exchange. The Overall Heat Transfer Coefficient is given by U = (18) Maximum Heat Transfer Rate is given by Q max = Cmin (T 1 - t 1 ) (19) Effectiveness is given by ε = (20) III. Result and Discussion A. The Theoretical Results are Discussed Below for Comparison of between Flat Plate Heat Exchanger and Hemispherical Fin Heat Exchanger. Fig. 9: Mass Flow Rate Vs Overall Heat Transfer Coefficient (Cold Fluid Mass Flow The fig. 9 shows the comparsion between plate heat exchanger and hemispherical fin plate heat exchanger when cold fluid mass flow rate is varied the graph shows a constant increase in overall heat transfer coefficient as the mass flow rate increases in both cases but the overall heat tranfer coefficient in case of hemispherical fin plate heat exchanger is higher compared to plate heat exchanger. Fig. 7: Mass Flow Rate Vs Heat Transfer (Cold Fluid Mass Flow The above graph fig. 7 shows the comparsion between plate heat exchanger and hemispherical fin plate heat exchanger when cold fluid mass flow rate is varied the graph shows a increase in heat transfer as the mass flow rate increases in both cases but the heat tranfer in case of hemispherical fin plate heat exchanger is higher compared to plate heat exchanger. Fig. 10: Mass Flow Rate Vs Overall Heat Transfer Coefficient (Hot Fluid Mass Flow The fig. 10 shows the comparsion between plate heat exchanger and hemispherical fin plate heat exchanger when hot fluid mass flow rate is varied the graph shows a constant increase in overall heat transfer coefficient as the mass flow rate increases in both cases but the overall heat tranfer coefficient in case of hemispherical fin plate heat exchanger is higher compared to plate heat exchanger. Fig. 8: Mass Flow Rate Vs Heat Transfer (Hot Fluid Mass Flow 12 International Journal of Research in Mechanical Engineering & Technology The results were plotted as graphs and were discussed. The theoretical analysis show that the overall heat transfer coefficient and heat transfer of hemispherical fin plate heat exchanger is higher compared to a flat plate heat exchanger when the mass flow rate of hot fluid is kept constant and cold is varied and when the mass flow rate of hot is varied and cold is kept constant.

5 ISSN : (Online) ISSN : (Print) B. The Comparison of Experimental and Theoretical Results Are Discussed Below For Hemispherical Fin Heat Exchanger. IJRMET Vo l. 7, Is s u e 2, Ma y - Oc t 2017 The above graph fig. 13 shows the theoretical and experimental value comparsion. The graph is plotted with mass flow rate vs overall heat transfer coefficient for hemispherical fin plate heat exchanger when cold fluid mass flow rate is varied the graph shows a little variation between theoretical and experimental value. Fig. 11: Mass Flow Rate Vs Heat Transfer (Cold Fluid Mass Flow The above graph fig. 11 shows the theoretical and experimental value comparsion. The graph is plotted with mass flow rate vs heat transfer for hemispherical fin plate heat exchanger when cold fluid mass flow rate is varied the graph shows a little variation between theoretical and experimental value. Fig. 14: Mass Flow Rate Vs Overall Heat Transfer Coefficient (Hot Fluid Mass Flow The above graph fig. 14 shows the theoretical and experimental value comparsion. The graph is plotted with mass flow rate vs overall heat transfer coefficient for hemispherical fin plate heat exchanger when hot fluid mass flow rate is varied the graph shows a little variation between theoretical and experimental value. Fig. 12: Mass Flow Rate Vs Heat Transfer (Hot Fluid Mass Flow The above graph fig. 12 shows the theoretical and experimental value comparsion. The graph is plotted with mass flow rate vs heat transfer for hemispherical fin plate heat exchanger when hot fluid mass flow rate is varied the graph shows a little variation between theoretical and experimental value. Fig. 15: Mass Flow Rate Vs Effectiveness (Cold Fluid Mass Flow The above graph fig. 15 shows the experimental effectiveness when cold fluid mass flow rate is varied the effectiveness decreases as the mass flow rate is increased. Fig. 13: Mass Flow Rate Vs Overall Heat Transfer Coefficient (Cold Fluid Mass Flow Fig. 16: Mass Flow Rate Vs Effectiveness (Hot Fluid Mass Flow w w w.i j r m e t.c o m International Journal of Research in Mechanical Engineering & Technology 13

6 IJRMET Vo l. 7, Is s u e 2, Ma y - Oc t 2017 ISSN : (Online) ISSN : (Print) The above graph fig. 16 shows the experimental effectiveness when hot fluid mass flow rate is varied the effectiveness decreases as the mass flow rate is increased. The results graphs were plotted and discussed. The theoretical and experimental analysis show that the overall heat transfer coefficient and heat transfer of hemispherical fin plate heat exchanger are in good agreement when compared with eachother. The effectiveness of the hemispherical fin heat exchanger calculated from experimental data shows that the effectiveness decreases when the mass flow of either cold or hot is kept constant and the other is varied. IV. Conclusion The area of the flat plate heat exchanger and hemispherical fin plate heat exchanger were calculated with equal dimensions. The result showed that the addition of fins increases the area. The hemispherical fin plate heat exchanger was compared with flat plate heat exchanger theoretical by varying the mass flow rate of one fluid and keeping the mass flow rate of other fluid constant. The theoretical results showed that the hemispherical fin plate heat exchanger has a higher heat transfer and overall heat transfer coefficient compared to flat plate heat exchanger. Thus a hemispherical fin heat exchanger was fabricated and tested experimental. When the mass flow rate of one fluid was kept constant and the mass flow rate of the other fluid varied there was a increase in heat transfer but the effectiveness decreased. The experimental results were compared with the theoretical results of hemispherical fin plate heat exchanger. The experimental results showed a good agreement with the theoretical results obtained for hemispherical fin heat exchanger. References [1] W.M. Kays, A.L. London,"Compact Heat Exchangers", third ed., McGraw-Hill, New York, [2] T.Kuppan,"Heat Exchanger Design Handbook", Marcel Dekker, Inc, New York, [3] Sadik Kakac, Homgtan Liu,"Heat Exchangers Selection, Rating and Thermal Design", second edition, CRC Press LLC, [4] José Fernández-Seara, Rubén Diz, Francisco J. Uhía Pressure drop and heat transfer characteristics of a titanium brazed plate-fin heat exchanger with offset strip fins, Applied Thermal Engineering 51, pp , [5] Mao-Yu Wena, Ching-Yen Ho, Heat-transfer enhancement in fin-and-tube heat exchanger with improved fin design, Applied Thermal Engineering 29, pp , [6] M. Khoshvaght-Aliabadi, F. Hormozi, A. Zamzamian Role of channel shape on performance of plate-fin heat exchangers: Experimental assessment, International Journal of Thermal Sciences 79, pp , [7] Yonghan Kim, Yongchan Kim, Heat transfer characteristics of flat plate finned-tube heat exchangers with large fin pitch, International Journal of Refrigeration 28, pp , [8] Praveen Pandey, Rozeena Praveen, S.N.Mishra Experimental investigation on the effect of fin pitch on the performance of plate type fins, IJRET, Vol. 1, Issue 3, pp , [9] Hao Peng, Xiang Ling, Juan Li, Performance investigation of an innovative offset strip fin arrays in compact heat exchangers, Energy Conversion and Management 80, pp , [10] Anjun Jiao, Seungwook Baek, Effects of distributor configuration on flow maldistribution in plate-fin heat exchangers, Heat Transfer Engineering 26, pp , [11] Masoud Asadi, Ramin Haghighi Khoshkhoo, Effects of mass flow rate in terms of pressure drop and heat transfer characteristics, Merit Research Journal of Environmental Science and Toxicology Vol. 1(1) pp , [12] Junqi Dong, Jiangping Chen, Zhijiu Chen, Wenfeng Zhang, Yimin Zhou, Heat transfer and pressure drop correlations for the multi-louvered fin compact heat exchangers, Energy Conversion and Management 48, pp , [13] Hui Han, Ya-Ling He, Yin-Shi Li, Yu Wang, Ming Wu, A numerical study on compact enhanced fin-and-tube heat exchangers with oval and circular tube configurations, International Journal of Heat and Mass Transfer 65, pp , [14] Ya-Ling He, Pan Chu, Wen-Quan Tao, Yu-Wen Zhang Analysis of heat transfer and pressure drop for fin-andtube heat exchangers with rectangular vortex generators, Applied Thermal Engineering 42, pp. 1-14, [15] Chan Hyeok Jeong, Hyung Rak Kim, Man Yeong Ha, Sung Wan Son, Jae Seok Lee, Pan Yeong Kim, Numerical investigation of thermal enhancement of plate fin type heat exchanger with creases and holes in construction machinery, Applied Thermal Engineering 62, pp , ANISH.A holding a position of Assistant professor in the Department Mechanical Engineering. He has been currently working as an Assistant Professor in Ponjesly College of Engineering Nagercoil for the last 3 years. He has completed his Master degree in Energy Engineering from Regional Centre of Anna University, Tirunelveli in the year He did his B.E in mechanical engineering from Cape Institute of Technology, Tirunelveli in the year He has also worked as an Erection Engineer for two years from 2010 to He is currently working in the field of solar energy and wind energy. ANUSH RAJ.B holding a position of Assistant professor in the Department Mechanical Engineering. He has been currently working as an Assistant Professor in Ponjesly College of Engineering Nagercoil for the last 3 years. He has completed his Master degree in Energy Engineering from Regional Centre of Anna University, Tirunelveli in the year He did his B.E in mechanical engineering from ST.XAVIER S COLLEGE OF ENGINEERING, Nagercoil in the year He is currently working in the field of solar energy and biomass energy. 14 International Journal of Research in Mechanical Engineering & Technology

7 ISSN : (Online) ISSN : (Print) IJRMET Vo l. 7, Is s u e 2, Ma y - Oc t 2017 RAJESH THIRUMALAI holding a position of Assistant professor in the Department Mechanical Engineering. He has been currently working as an Assistant Professor in Ponjesly College of Engineering Nagercoil for the last 4 years. He has completed his Master degree in Thermal Engineering from Ponjesly College of Engineering, Nagercoil in the year He did his B.E in mechanical engineering from Cape Institute of Technology, Tirunelveli in the year He has also worked as an Erection Engineer for two years from 2010 to He is currently working in the field of Thermal and Heat Exchangers. w w w.i j r m e t.c o m International Journal of Research in Mechanical Engineering & Technology 15