IJSRD - International Journal for Scientific Research & Developent Vol. 3, Issue 3, 215 ISSN (online): 2321-613 Theral Perforance of Waste Heat Recovery by using TPCT Heat Exchanger Charged with Nanofluid Akash shetty 1 Nikhil Shedge 2 Akshay Talekar 3 Zakar Shirawale 4 Rahul Pise 5 1,2 Navsahyadri Education Society s Group of Institutions, Pune Abstract Hot air plays an iport role in ode life. The consuption of hot air represents a significant part of the nation's energy consuption. One way of reducing the energy consuption involved, and hence the cost of that energy, is to reclai heat fro the waste war air that is discharged to the sewer each day. The potential for econoic waste air heat recovery depends on both the quantity available and whether the quality fits the requireent of the heating load. To recover heat fro waste air in residential and coercial buildings is hard to achieve in quality because of its low teperature range. Nevertheless, efforts to recycle this waste energy could result insignificant energy savings. The objective of this research was to develop a two phase closed therosyphon heat exchanger charged with nanofluid for a waste air heat recovery syste. The advantage of the syste proposed in this work is that it provides useful energy transfer during siultaneous flow of cold supply and war drain air. While this concept is not new, the design of the TPCT heat exchanger with nanofluid for the present study is significantly different fro those used previously. Coponent experients were carried out to deterine the perforance characteristics of a heat pipe heat exchanger charged with nanofluid. By replacing the conventional fluid in heat pipe with CuO/H2O nanofluid (2% volue fraction) of the heat pipe heat exchanger good perforance can be obtained. The axiu effectiveness obtained for proposed TPCT CuO/H2O charged nanofluid heat exchanger is.2862 (2% volue fraction copared with effectiveness.16 obtained with conventional heat pipe working fluid. The influence of ass flow rate and source teperature on effectiveness of TPCTHX exhibits sae pattern as that of conventional working fluid. The axiu enhanceent in effectiveness obtained is 35%.Thus the nanofluid as working fluid in TPCT enhances the effectiveness of heat exchanger. Key words: TPCT, Nanofluid I. INTRODUCTION Hot air plays an iport role in ode life. The consuption of hot air represents a significant part of the nation's energy consuption. One way of reducing the energy consuption involved, and hence the cost of that energy, is to reclai heat fro the waste war air that is discharged to the sewer each day. The potential for econoic waste air heat recovery depends on both the quantity available and whether the quality fits the requireent of the heating load. To recover heat fro waste air in residential and coercial buildings is hard to achieve in quality because of its low teperature range. Nevertheless, efforts to recycle this waste energy could result insignificant energy savings. The objective of this research is to develop a two phase closed therosyphon heat exchanger charged with nanofluid for a waste air heat recovery syste. The advantage of the syste proposed in this work is that it provides useful energy transfer during siultaneous flow of cold supply and war drain air. While this concept is not new, the design of the TPCT heat exchanger with nanofluid for the present study is significantly different fro those used previously. Coponent experients were carried out to deterine the perforance characteristics of a heat pipe heat exchanger charged with nanofluid. By replacing the conventional fluid in heat pipe with CuO/H2 nanofluid (2% volue fraction) of the heat pipe heat exchanger good perforance can be obtained. The axiu effectiveness obtained for proposed TPCT CuO/H2 charged nanofluid heat exchanger is.2862 (2% volue fraction copared with effectiveness.16 obtained with conventional heat pipe working fluid. The influence of ass flow rate and source teperature on effectiveness of TPCT HX exhibits sae pattern as that of conventional working fluid. The axiu enhanceent in effectiveness obtained is 35.6%. Thus the nanofluid as working fluid in TPCT enhances the effectiveness of heat exchanger. II. LITERATURE SURVEY Yodraket et al. [1] studied heat recovery syste at Furnace in a Hot Forging Process; he concluded that the experient findings indicated that when the hot gas teperature increased, the heat transfer rate also increased. If the internal diaeter increased, the heat transfer rate increased and when the tube arrangeent changed fro inline to staggered arrangeent, the heat transfer rate increased. The heat pipe air-preheated can reduced the quantity of using gas in the furnace and achieve energy thrift effectively. Noie-Baghbanet et al. [2] carried out the research on the theory, design and construction of heat pipes, especially their use in heat pipe heat exchangers for energy recovery, reduction of air pollution and environental conservation. A heat pipe heat exchanger has been designed and constructed for heat recovery in hospital and laboratories, where the air ust be changed up to 4 ties per hour. In This research, the characteristic design and heat transfer liitations of single heat pipes for three types of wick and three working fluids have been investigated, initially through coputer siulation. Construction of heat pipes, including washing, inserting the wick, creating the vacuu, injecting the fluid and installation have also been carried out. After obtaining the appropriate heat flux, the airto-air heat pipe heat exchanger was designed, constructed and tested under low teperature (15±55C) operating conditions, using ethanol as the working fluid. Experiental results for absorbed heat by the evaporator section are very close to the heat transfer rate obtained fro coputer siulation. Saan et al. [9] exained the possible use of a heat pipe heat exchanger for indirect evaporative cooling as well as heat recovery for fresh air preheating. Theral All rights reserved by www.ijsrd.co 1939
perforance of a heat exchanger consisting of 48 therosyphon arranged in six rows was evaluated. The tests were carried out in a test rig where the teperature and huidity of both air streas could be controlled and onitored before and after the heat exchanger. Evaporative cooling was achieved by spraying the condenser sections of the therosyphon. The paraeters considered include the wetting arrangeent of the condenser section, flow ratio of the two streas, initial teperature of the priary strea and the inclination angle of the therosyphon. Their results showed that indirect evaporative cooling using this arrangeent reduces the fresh air teperature by several degrees below the teperature drop using dry air alone. Huidity control is a never-ending war in tropical hot and huid built environent. Heat pipes are passive coponents used to iprove dehuidification by coercial forced-air HVAC systes. They are installed with one end upstrea of the evaporator coil to pre-cool supply air and one downstrea to re-heat supply air. This allows the syste's cooling coil to operate at a lower teperature, increasing the syste latent cooling capability. Heat rejected by the downstrea coil reheats the supply air, eliinating the need for a dedicated reheat coil. Heat pipes can increase latent cooling by 25-5% depending upon the application. Conversely, since the reheat function increases the supply air teperature relative to a conventional syste, a heat pipe will typically reduce sensible capacity. In soe applications, individual heat pipe circuits can be controlled with solenoid valves to provide iproved latent cooling control. Priary applications are liited to hot and huid cliates and where high levels of outdoor air or low indoor huidity are needed. Hospitals, superarkets and laboratories are often good heat pipe applications. Yauet et al. [1] entioned that for any years, heat pipe heat exchangers (HPHEs) with two-phase closed therosyphon, and has been widely applied as dehuidification enhanceent and energy savings device in HVAC systes. Coponents used to iprove dehuidification by coercial forced-air HVAC systes. They are installed with one end upstrea of the evaporator coil to pre-cool supply air and one downstrea to re-heat supply air. This allows the syste's cooling coil to operate at a lower teperature, increasing the syste latent cooling capability. Heat rejected by the downstrea coil reheats the supply air, eliinating the need for a dedicated reheat coil. Heat pipes can increase latent cooling by 25-5% depending upon the application. Conversely, since the reheat function increases the supply air teperature relative to a conventional syste, a heat pipe will typically reduce sensible capacity. In soe applications, individual heat pipe circuits can be controlled with solenoid valves to provide iproved latent cooling control. Priary applications are liited to hot and huid cliates and where high levels of outdoor air or low indoor huidity are needed. Hospitals, superarkets and laboratories are often good heat pipe applications. Mousa et al. [1]carried out an experiental study on an effect of nanofluid in Circular Heat Pipe. The nanofluid consisted of Al2O3 nanoparticles with a diaeter of 1 n. The experiental data of the nanofluids were copared with those of DI water including the wall teperatures and the total heat resistances of the heat pipe. Experiental results showed that if concentration of the nanofluid increasing, then the theral resistance of heat pipe decreased. Shang et al. [18] investigated the heat transfer characteristics of a closed loop OHP with Cu water nanofluids as the working fluid different filling ratios. The results were copared with those of the sae heat pipe with distilled water as the working fluid. The experiental results are confired that the use of Cu water nanofluids in the heat pipe could enhance the axiu heat reoval capacity by 83%. It was confored that directly adding nanoparticles into distilled water without any stabilizing agents had greater heat transfer enhanceent copared to the case where a stabilizing agent was added to the distilled water. III. DESIGN AND DEVELOPMENT OF EXPERIMENTAL SETUP As described earlier proposed work ais to investigate of experiental perforance of heat pipe heat exchanger charged with CuO/H2 Nanofluid under variable source teperatures and ass flow rate. With broad perspective this study ais to investigate the feasibility of heat pipe fro low teperature waste heat source. In order to achieve the objectives stated above it has been decided to design and develop the experiental syste as shown in following Figure 1. Heat pipe heat exchangers are devices that ade the exchange of energy (waste heat) fro a waste heat source to a colder source. Figure 1 shows the scheatic diagra of the experiental syste. The syste is coposed of three ajor parts: air heater (for waste hot air preparation), heat pipe heat exchanger and devices for easureent and control of paraeters. In the installation there are two circulating fluids: the hot agent (waste air) in the lower chaber of the heat exchanger and the cold agent (cold air) in the upper chaber of the heat exchanger. The heat pipe heat exchanger was equipped with eight heat pipes arranged vertically at an angle of 9 (Figure1). The working fluid used in heat pipe is CuO/H2O nanofluid. All rights reserved by www.ijsrd.co 194
Fig 1: Scheatic layout of proposed experiental syste Fig. 2: 3D Representation of Experiental Set Up IV. DESIGN AND DEVELOPMENT OF HEAT PIPE HEAT EXCHANGER Heat pipe diensions is choose as per below table. While designing heat pipe it has to be undergoes under liit checking. Theral properties of CuO nanofluid are selected fro various sources and it is used for calculation heat pipe liit. By using various correlations fro literature survey heat flux under various liits is calculated for checking safety of design of heat pipe. Sr. Notat Valu Uni Paraeters No ion e t.2 1 Evaporator Length L v 5 2 Adiabatic Length L add.5.2 3 Condenser Length L c 5 4 Total Length L t.6 5 Effective Length L eff.55 6 Inner Radius r i Cross Section Area A 15 2 8 Axial Angle Ø 9 O 9 Theral Conductivity of W/ λ 385 Material (Copper) k 1 Vapour Core Radius r v 11 Evaporative Section Radius r e 12 Condenser Section Radius r c All rights reserved by www.ijsrd.co 1941
13 14 Nano Particle Volue -.2 - Fraction Density of Nanoparticle kg/ ρ np (CuO) 21 3 Table-1: Heat pipe paraeters A. Heat Pipe Liit Calculation Heat pipes undergo various heat transfer liitations depending on the working fluid, the diensions of the heat pipe, and the heat pipe operational teperature. 1) Viscous liitation: The viscous liit occurs at low operating teperatures, where the saturation vapour pressure ay be of the sae order of agnitude as the pressure drop required driving the vapour flow in the heat pipe. This results in an insufficient pressure available to drive the vapour. The viscous liit is soeties called the vapour pressure liit (4.2) 2) Sonic liitation: The sonic liit is due to the fact that at low vapour densities, the corresponding ass flow rate in the heat pipe ay result in very high vapour velocities, and the occurrence of choked flow in the vapour passage ay be possible. (4.3) 3) Entrainent liitation: The entrainent liit refers to the case of high shear forces developed as the vapour passes in the counter flow direction over the liquid saturated wick, where the liquid ay be entrained by the vapour and returned to the condenser. This results in insufficient liquid flow of the wick structure. (4.4) 4) Boiling liitation: The boiling liit occurs when the applied evaporator heat flux is sufficient to cause nucleate boiling in the evaporator wick. This creates vapor bubbles that partially block the liquid return and can lead to evaporator wick dry out. The boiling liit is soeties referred to as the heat flux liit. Tep C Sonic Liit kw/ 2 Viscous liit kw/ 2 ( ) (4.5) Entrainent Liit kw/ 2 Boiling Liit kw/ 2 2.5.5512.8549 1.5 4..5.815 1.2 6.89.96.9.95 8 1.1 1.13.353.5 Table-2: Heat Pipes Liits for Various Operating Teperatures It has been noticed that the aount of wattage to be transferred to which heat pipe is designed is below the axiu axial heat flux for variable teperature and thus design of heat pipe were observed to be successful. Fig. 3: Heat Pipes Liits for Various Operating Teperatures V. EXPERIMENTATION A. Test Methodology: 1) In order to investigate the theral perforance of TPCT heat recovery heat exchanger charged with nanofluid under variable source teperature and ass low rate, it has been decided to vary the heat input fro 25 to 1 W in the step of 25 W. The ass flow rate is varied fro 1 cf to 4 cf in the step of 1 cf. 2) For a particular heat input the ass flow rate of hot and cold air streas are varied fro 1 to 4 cf as entioned above. 3) At steady state the hot and cold air strea inlet and outlet teperatures across heat pipe heat exchanger is easured. 4) The corresponding volteter and aeter readings are noted and power supplied to electrical heater is calculated. 5) Air velocity is easured with the help of air vane aneoeter. B. Test Paraeters: Experientation was carried on the TPCT HRHX. Working fluid is iportant paraeter in the experientation. CuO/H2O nanofluid was used as a working fluid. Other paraeters and its description are as follows. Paraeter Description Heat load (W) 25 W to 1 W Source teperature up to 65 C Mass flow rate ().512 to.249 kg/s Discharge of Blower 1 to 4 cf Velocity 1.4 to 5.24 /s Table-3: Test Paraeters The heat input, effectiveness of heat exchanger is calculated by the following equations. (W) Where, V= Voltage, I=Current Effectiveness of heat exchanger = Qactual/ Q ax Heat transfer coefficient can be calculated by using equation Q= h A ΔT All rights reserved by www.ijsrd.co 1942
Inlet Tep in C Effectiveness ΔT Inlet Tep in C VI. RESULT AND DISCUSSION The experiental perforance of heat pipe heat exchanger was experientally evaluated. Experientation was carried out to investigate the effect of heat input and ass flow rate of hot and cold air streas on the effectiveness of heat exchanger. On the basis of the observations recorded the effectiveness of heat exchanger for particular heat input and ass flow rate of hot and cold air streas were calculated. For given heat input with increase in ass flow rate of air the teperature difference decreases. The nuerical and graphical variation of the teperature difference is shown in Figure 4. 14 12 1 8 6 4 2 Variation in ΔT at Evaporator section.4.94.142.189 Hot air strea flow rate (3/s) 25W 5W 5W 1W Fig. 4: Variation in ΔT at Evaporator Section For given heat input with increase in ass flow rate of air the teperature difference decreases. The nuerical and graphical variation of the teperature difference is shown in Figure 5. Fig. 6: Variation in Inlet Teperature at Evaporator Section Variation in outlet teperature of evaporator section is observed due to the absorption of the heat by heat pipe working fluid during the phase change. At evaporator section working fluid absorbs the heat and it gets evaporated. So at the outlet of evaporation section teperature decrease and Figure shows the variations. 6 5 4 3 2 1 Variation in outlet teperature at evaporator section.4.94.142.189 25W 5W 5W 1W Hot air strea flow rate (3/s) Fig. : Variation in Outlet Teperature at Evaporator Section With increase in heat input the teperature at the outlet of condenser section increases. Figure 8 shows variation in outlet teperature at condenser section. Fig. 5: Variation in ΔT at Condenser Section Variation in inlet teperature at evaporator section is observed due to the heat input supplied to the fin tube heater with increase in heat input, teperature at inlet of evaporator section increases and Figure 6 shows the variations. 8 6 5 4 3 2 1 Variation in inlet teperature at evaporator section.4.94.142.189 Hot air strea flow rate (3/s) 25W 5W 5W 1W Fig. 8: Variation in Outlet Teperature at Condenser Section Figure 9 shows the variation in the effectiveness at evaporator section of heat exchanger with variation in heat input. It is observed that the effectiveness of two phase closed therosyphon charged with nanofluid increases with increase in heat input for a particular air strea flow..35.3.25.2.15.1.5 Variation in effectiveness of HX with heat input.419.9438.1415.1886 25W 5W 5W 1W Air strea flow rate ( 3 /s) Fig. 9: Variation in Effectiveness of HX with Heat Input All rights reserved by www.ijsrd.co 1943
Heat Transfer Coefficient Figure 1 shows the variation in the effectiveness of heat exchanger at condenser section with variation in heat input. It is observed that the effectiveness of two phase closed therosyphon charged with nanofluid increases with increase in heat input for a particular air strea flow. 6 5 4 3 2 1 Variation in Heat Transfer Coefficient of HX with heat input 1.5 /s 2.1 /s 3.15 /s 4.19 /s 25 5 5 1 Heat Input (W) Fig. 1: Variation in Heat Transfer Coefficient of HX with Heat Input Figure 11 shows the variation in the Nusselt Nuber at evaporator section of heat exchanger with variation in heat input. It is observed that the effectiveness of two phase closed therosyphon charged with nanofluid increases with increase in heat input for a particular air strea flow. Fig. 11: Variation in Nusselt Nuber of HX with Heat Input 1) The perforance of heat pipe heat exchanger charged with CuO/H2 nanofluid increases with increase in source teperature. 2) Maxiu effectiveness observed for proposed heat pipe heat exchanger is up to.32. 3) The results obtained for TPCT heat exchanger charged CuO/H2 nanofluid are superior with that of TPCT charged with conventional fluid. 4) Enhanceent in effectiveness of heat exchanger for current study is about 35% copared with the available literature. 5) Iproveent in effectiveness of two phase closed therosyphon heat exchanger charged with nanofluid is due to theral conductivity enhanceent of nanofluid. 6) TPCT heat recovery heat pipe heat exchanger can be suitably eployed for heat recovery fro low source teperature. REFERENCES [1] YodrakL., Sapan R., Waste Heat Recovery by Heat Pipe Air-Preheater to EnergyThrift fro the Furnace in a Hot Forging Process, Aerican Journal of Applied Sciences21. (5),pp65-681. [2] Noie-Baghban,MajideianG., Waste heat recovery using heat pipe heat exchanger(hphe) for surgery roos in hospitals, Journal of Applied Theral Engineering, 2, pp 121-1282,. [3] SaanW. Perforance of a therosyphon heat exchanger in an evaporative air conditioning syste, Proc. 5th Australasian heat & Mass Transfer Conference, Brisbane, 1993. [4] Yau Y., TuckerA., The perforance study of a wet sixrow heat pipe heat exchanger operating in tropical buildings, International Journal of Energy Research 2, 23, pp,18-22. [5] MousaM., Effect of nanofluid concentration on the perforance of circular heat pipe,ains Shas Engineering Journal (211) 2, pp. 63-69 [6] Shang X.,Liu Z., Heat transfer perforance of a horizontal icro grooved heat pipe using CuOnanofluid, Microechanics and Micro engineering 18 (28),pp. 35 3. VII. CONCLUSION The experiental investigation was carried out on two phase closed therosyphon heat pipe heat exchanger charged with CuO/H2 nanofluid. The effect of source teperature and ass flow rate of hot and cold air streas on effectiveness of nanofluid charged TPCT heat exchanger was experientally investigated. The heat input to finned tube air heater was varied fro 25 W to 1 W and hot and cold air strea flow rate varied fro.419 3 /s to.236 3 /s. The effect of variation in source teperature and ass flow rate of hot and cold air streas on effectiveness of heat exchanger was experientally studied. The heat pipes used in heat exchanger was specially designed for heat recovery application. Conclusions fro studied experient are as follows, All rights reserved by www.ijsrd.co 1944