Volume 115 No. 7 2017, 349-354 ISSN: 1311-8080 (printed version); ISSN: 1314-3395 (on-line version) url: http://www.ijpam.eu ijpam.eu ENHANCEMENT OF HEAT TRANSFER USING NANO-REFRIGERANT Tumuluri Kanthimathi 1, Arimanda Teja 2*, Dandamudi Pardha Saradhi 3, Kovvuri Satya Sai Aditya Reddy 4, KompalliSomasai Kumar 5. 1,2,3,4,5 Department of Mechanical Engineering, K L University, India * Corresponding author s Email: ateja200@gmail.com Abstract: Nano refrigerants are special type of nano fluids that are synthesized by mixing or dispersing nanoparticles in refrigerants. They are relatively new with respect to other nano fluids and have broad range of application in refrigeration, air-conditioning systems and other heat transfer devices due to their enhanced heat transfer characteristics. In this paper coefficient of heat transfer of nano refrigerant is investigated based on different volume concentrations of Al2O3 nanoparticles are suspended in R134A. Correlations from existing studies have been used to determine thermo- physical properties like thermal conduction, viscosity, density and specific heat of nano-refrigerant. Study has been conducted by theoretical calculations for calculation of total heat transfer co-efficient. Results from the current study shows total heat transfer co-efficient, thermal conductivity increases and specific heat decreases with increase in particle concentration. 1. Introduction Nano refrigerants are special type of nano fluids that are synthesized by mixing or dispersing nanoparticles in refrigerants. The most widely recognized refrigerant in refrigeration systems is R132a. But, as a result of rapid industrialization the need of new refrigerants which has ability to take more heat from the system has increased. Thus, we require something new that will have the capacity to supplant elective refrigerant with some advanced thermophysical properties like Thermal Conductivity, Specific heat, Viscosity, Density etc. In order to meet the expectations of the Industries, opportunities to increase the heat exchange are given by concentrating attention on the fluid performance. A new technology have been developed,it is combination of nanoparticles with the refrigerants called as nanorefrigerents. The use of nano refrigerants have created a massive boost in the efficiency of the heat exchangers. These nano refrigerants have high thermophysical properties compared to the base refrigerants. These properties depends on the Concentration of nanoparticles, mixing process of nanoparticles with refrigerants, size of nanoparticles, temperature at which nanoparticle is chosen. The most used nanoparticles mixed in refrigerants is Al2O3 because this nanoparticles are available in reasonable prices and capability of mixing with refrigerants is comparatively very high. Nomenclature Symbol Description Units c p1 Specific heat of base fluid J/kg k c p2 Specific heat of nano fluidj/kg k c p Specific heat of nanorefrigerent J/kg k k Thermal conductivity nano refrigerant w/m k k 1 Thermal conductivity base fluid w/m k k 2 Thermal conductivity nano fluid w/m k µ Viscosity of nano refrigerant kg/m s ρdensity of nano refrigerant kg/m^3 ρ 1 Density of base fluid kg/m^3 ρ 2 Density of nano fluid kg/m^3 C Volume fraction 2. Literature Review Wang-1999[1] In this paper thermal conductivities of fluids mixed with Al2O3, Cuonano particles mixed in water, engine oil, and ethylene glycol are measured. Conclusions are made that thermal conductivity of nanoparticle increases with decreasing the particle size and nanofuid mixture is dependent on the microscopic motion and the particle structure of nano particles. N. Subramani- 2011 [2] Conclusions are made that power utilization of the compressor decreases by 25% when the nano lubricant is utilized rather than ordinary oil and the coefficient of performance of the refrigeration system increments by 33% when the nano refrigerant is utilized. N. Subramani-2013 [3] The outcomes shows that refrigeration system with nano lubricant works regularly and securely. It is found that power utilization decreases by 15.4% and the coefficient of performance increments by 20% when TiO2 is utilized in place of SUNISO 3GS. Teshome Bekele Kotu-2013 [4] In this paper test on double pipe heat exchanger with the air refrigeration system was performered. The power use of the HFC134a blended with mineral oil and DPHE system was diminished by 30% and HFC134a blended 349
with mineral oil and alumina nanoparticle was decreased by 26% when compared and normal one. R. Reji Kumar-2013 [5] Conclusions are made that study demonstrates the power utilization of the compressor lessens by 11.5% when the nanolubricant is utilized rather than ordinary oil and coefficient of performance of the refrigeration system likewise increments by 19.6 % when the customary POE oil is replaced with nano refrigerant. T. Coumaressin-2014 [6] Conclusions from the study are made that Cuo nanoparticle with R134a refrigerant can be used as excellent refrigerant to improve the heat transfer characteristics for different concentrations of Cu0 nanoparticle using CFD analysis. Harish Kumar Patel-2014 [7] In this paper thermal conductivity of nano fluids are studied and conclusions are made that nano fluid can be good replacement for conventional base fluid as thermal conductivity of nano fluid changes according to the temperature and volume concentration of the nano particles. Results shown that thermal conductivity increases with increase in temperature and decrease of specificheat of nano fluid is observed. Parvinder Singh-2015 [8] This paper is focusing on mixing ofdifferent volume concentration of nano particles with refrigerants and performance characteristics of the system are drawn. The results shows the comparision of actual and theoretical values of performance characteristics of the system while using nanorefrigrants. Rahul.K. Jaiswal-2015 [9] In this paper it is observed that using nano refrigerant instead of pure refrigerant in vapour compression refrigeration cycle increase the performance of system and also observed that the nanoparticle mixed in pure refrigerant enhance the thermal conductivity from 10 to 95 % and heat transfer enhancement factor ranges from 1.4 to 2.5. Asif Faizan- 2016 [10] Coclusions of the study are thermal conductivity,dynamic viscosity increases with increase in volume concentration and Specific heat increases with increase in temperature and density decreases with increase in temperature for nano refrigerant R245fa/ 3. Methodolgy Al2O3 nanoparticles are chosen to study the thermophysical properties when combined with the refrigerant. The properties of the refrigerant taken R134a and Al2O3 nanoparticles are tabulated below. The analysis is carried out at the room temperature of 25 degrees Celsius for the volume concentrations of 0.05%, 0.07%, 0.1%, 0.5%, 1% respectively. All the calculations are done based on the literature Survey. Table 1. Properties of R134a and Al2O3 Property R134a Al2O3 Density 4.25 Kg/m^3 3690 Kg/m^3 Thermal Conductivity 0.0824 w/m.k 40 w/m.k Viscosity 0.202 1450 centipoise Centipoise Specific Heat 142.5 J/kg.K 880 J/Kg.K 3.1. Mathematical Models The following equations are used to calculate the thermal properties of nano refrigerant Specific heat of nanorefrigerent c p = (1-C) c p1 + C c p2 Thermal conductivity nano refrigerant k = k 1 [(k 2 +2k 1-2C(k 1 -k 2 )) / (k 2 +2k 1 +C (k 1 -k 2 ))] Viscosity of nano refrigerant µ = µ 1 [1 / (1- C)^ 2.5] Density of nano refrigerant ρ = (1- C) ρ 1 + C ρ 2, 3.2 Numerical Analysis The work is conducted to evaluate the heat transfer coefficient of the nano refrigerant with increasing volume concentrations of nanoparticles in the refrigerant. The conclusions are made that the specific heat is increasing with increase in volume concentrations. The results are tabulated below. Table 2. Properties of Al2O3 for various Concentrations Property 0.05% 0.07% 0.1% 0.5% Specific Heat Thermal Conductivity Viscosity (kg/m s) Density (kg/m^3) 142.47 142.46 142.44 142.22 0.08252 0.0825 7 0.0826 0.0836 0 22 023 025 04 6.09 6.83 7.93 22.67 350
Table 3. Properties of Al2O3 for various Concentrations Property 1% 2% 3% 4% Specific Heat 141.87 141.41 140.86 140.36 Thermal 0.0839 0.0873 0.0899 0.0926 Conductivity Viscosity (kg/m s) 07 124 179 237 Density (kg/m^3) 41.10 77.465 114.77 151.68 Graph 3. Density Vs Al2O3 volume Concentration. 4. Results and Discussion We found that as the volume concentrations are increasing the Specific heat of the nano refrigerant is decreasing and the Thermal Conductivity is increasing. The results are shown below. Graph 4. Viscosity Vs Al2O3 volume Concentration. 4.1 Analysis Graph 1. Thermal Conductivity Vs Al2O3 volume Concentration Heat Transfer characters should be enhanced to get optimal results. By adding nanoparticles to the refrigerant we found out output temperatures to study the heat transfer rate. In the circular section at room temperature of 25 degrees Celsius. A constant heat flux is applied to study the its effect on output temperatures. As we increase the volume concentrations of the nanoparticles in the refrigerant, the output temperatures of the circular section decreased. Graph 2. Specific Heat Vs Al2O3 volume Concentration. Figure 1. Outlet Temperature for R134a 351
Figure 2. Outlet Temperature for R134a and 0.07% Figure 5. Outlet Temperature for R134a and 1% Figure 3. Outlet Temperature for R134a and 0.05% Figure 6. Outlet Temperature for R134a and 2% Figure 4. Outlet Temperature for R134a and 0.1% Figure 7. Outlet Temperature for R134a and 3% 352
4. Conclusion We concluded that as the volume concentration of the nano refrigerant is increasing the heat transfer coefficient increases. The addition of Al2O3 in the refrigerant improves the efficiency of the refrigerant. Thus, improves the overall efficiency of Heat Exchanger. References Figure 8. Outlet Temperature for R134a and 4% By analysing the results we concluded that as the volume concentration of the nano refrigerant is increasing the heat transfer coefficient increases. This shows that as the concentration of Al2O3 increases the refrigerant can observe more heat. The values of Heat Transfer coefficient is tabulated below. Table 4. Heat Transfer Co-efficient Values Concentration Heat Transfer Coefficient (w/m^2.k) 0.05% 433.82 0.07% 486.50 0.1% 564.77 0.5% 1612.06 1% 2915.43 2% 5477.78 3% 8086.25 4% 10645.21 [1] Xinwei Wang and Xianfan Xu Purdue, on Thermal Conductivity of Nanoparticle Fluid Mixture. October December 1999. [2] N. Subramani 1, M. J. Prakash, on Experimental studies on a vapour compression system using nano refrigerants 2011. [3] Subramani.N, Aswin Mohan, Dr.JosePrakash.M, on Performance Studies on Vapour Compression Refrigeration System Using Nano-Lubricant 12 to 14 december 2013. [4] Teshome Bekele Kotu& R. Reji Kumar, on Comparison of Heat Transfer Performance In Domestic Refrigerator Using Nano refrigerant And Double Pipe Heat Exchanger 2013. [5] R. Reji Kumar, K. Sridhar, M.Narasimha, on Heat transfer enhancement in domestic refrigerator using R600a/mineral oil/nano-al2o3 as working fluid 2013. [6] T. Coumaressin and K. Palaniradja, on Performance Analysis of a Refrigeration System Using Nano Fluid 2014. [7] Harish Kumar Patel, Dr.V.N.Bartaria, Review and Experimental Comparison of Al2O3and Water Mixture Based Nano fluid Thermal Conductivity as Heat Transfer Fluid 9, September 2014. [8] Parvindarsingh, To Study The Application Of Nano refrigerant In Refrigeration System : A Review 2015. Graph 5. Heat Transfer Co-efficient Vs Al2O3 Volume Concentration. [9] A.P. Vetrivel, S.Senthilkumaren, G. Sakthinathan, R.Anandhan, Review for The Heat Transfer Enhancement of Heat Exchanger Using Nano fluids August 2016. [10] Asif Faizan, Dong Han, Thermophysical Property and Heat transfer Analysis of R245fa/Al2O3 Nano refrigerant 2016. 353
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