ANALYSIS OF A BUBBLE PUMP DRIVEN ABSORPTION REFRIGERATION SYSTEM (EINSTEIN-SZILARD REFRIGERATOR VARIANT)

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1 International Journal of Mechanical Engineering and Technology (IJMET) Volue 7, Issue 6, Noveber Deceber 2016, pp , Article ID: IJMET_07_06_042 Available online at ISSN Print: and ISSN Online: IAEME Publication ANALYSIS OF A BUBBLE PUMP DRIVEN ABSORPTION REFRIGERATION SYSTEM (EINSTEIN-SZILARD REFRIGERATOR VARIANT) Shoaib Ahed, N Jayakrishnan, S Ganesh and Reuben George Mathew Departent of Mechanical Engineering, College of Engineering Trivandru, Thiruvanathapura, Kerala. India. ABSTRACT In the present work an attept has been ade to experientally investigate the theoretical perforance of a variant of an Einstein-Szilard Refrigerator. The refrigerator studied requires only heat input for its working and uses a bubble pup. Analysis involving conservation of ass and first law of therodynaics were carried out to calculate COP, capacity and energy requireent of the syste. The analysis proved the effective working of this variant of the absorption refrigerator with an COP of Key words: Absorption refrigerator, Einstein-Szilard Refrigerator variant, ass flow analysis Cite this Article: Shoaib Ahed, N Jayakrishnan, S Ganesh and Reuben George Mathew, Analysis of a Bubble Pup Driven Absorption Refrigeration Syste (Einstein-Szilard Refrigerator Variant). International Journal of Mechanical Engineering and Technology, 7(6), 2016, pp INTRODUCTION Current refrigeration cycles used in air conditioning, refrigeration, and heat pup systes are two-pressure cycles. The teperature difference between the condenser and the evaporator is established by a pressure difference that is produced by a copressor in a copression cycles or a solution pup in absorption cycles. These two-pressure cycles require echanical devices with oving parts and access to electrical power. The copressor or pup adds significantly to the syste costs, reduces reliability, generates noise, requires energy and liits portability. The diffusion absorption refrigeration (DAR) cycle invented in the 1920s by Platen and Munters is based on the aonia/water ixture as working fluids and uses hydrogen as an auxiliary inert gas to establish a lower refrigerant partial pressure in the evaporator, while aintaining a higher refrigerant pressure in the condenser. Its efficiency is lower copared to the bi-pressure absorption cycles. It has liited coercial applications; it is used specially in the hotel roo refrigerators. In 1930, Einstein and Szilard obtained a US patent for another single pressure absorption refrigeration cycle. This cycle consists of a generator, a cobined condenser/ absorber, an evaporator, a pre-cooler and a solution heat exchanger. It operates with butane as a refrigerant, aonia as a pressure equalizing inert gas, and water as absorbent

2 Shoaib Ahed, N Jayakrishnan, S Ganesh and Reuben George Mathew 2. CYCLE DESCRIPTION The variation of the Einstein refrigeration cycle studied in this work can be described as follows: Liquid butane and aonia vapour flow into the evaporator (see Fig. 1). The butane vaporizes into the aonia and takes heat fro the refrigerated space. The aonia controls the saturation pressure of the butane. The gas-vapour ixture fored by aonia and butane leaves the evaporator and then passes through a heat exchanger where it is preheated. Then the ixture goes into the absorber-condenser. A strea of water flows into this vessel. Aonia vapor is absorbed in this water strea and heat is released by the process Figure 1 Original patent diagra The absorber-condenser is cooled to reove this heat and the heat released by the continuous condensation of the butane fed to the vessel. The condensed butane leaves the absorber-condenser, passes through a preheater and returns to the evaporator. The aonia strong solution is preheated and then it goes into the generator. The aonia strong solution is boiled in the generator to split off aonia fro water. The aonia weak solution is preheated and then flows into the accuulator. In the accuulator water and aonia are further separated and water is returned to the absorber condenser after losing ore heat. Pure aonia goes thru a heat exchanger where it losses heat and then goes into the evaporator. The Einstein refrigeration cycle does not need a echanical energy input to induce otion, input which is required by traditional absorption cycles. Instead, the Einstein cycle uses a bubble pup, a device driven by theral energy that is part of the generator. It is iportant to note that, although the Einstein cycle works with aonia, water and butane, the only substances that can for a liquid solution are aonia and water; aonia is alost iiscible in liquid butane, and butane and water are not iscible at all. Therefore, the liquid ixtures present in the Einstein refrigeration device can be treated as binary systes

3 Analysis of a Bubble Pup Driven Absorption Refrigeration Syste (Einstein-Szilard Refrigerator Variant) Figure 2 Block diagra of proposed syste 3. ANALYSIS 3.1 Assuptions The Pressure of the syste is fixed at 4 bar. The syste is considered to be under steady state while perforing ass flow and first law analysis. The behavior of Aonia-Butane ixture in the evaporator is assued to be azeotropic in nature. Since the pressure of the syste is 4 bar, the aonia-butane ixture condenses at 315 K, hence the teperature of condenser is assued to be 315K. The Teperature of the generator is assued to be 375K. The Aonia-Butane ixture for the sae assued syste pressure boils as low as 266K, hence teperature of the evaporator=266k 3.2 Therodynaic Properties of Working Fluids The Patel-Teja cubic equation of state, fitted to experiental data, is used for all fluid odeling (pure substances and ixtures). For the aonia-butane ixture, the Patel-Teja equation of state predicts vapor- in the evaporator. liquid-liquid equilibriu and azeotropic behavior at the pressures and teperatures Experiental easureents on the aonia butane syste verify this and the equation of state was fit to the experiental data. 3.3 Syste Coponents Modeling All coponents in the syste shown in Fig. (1) are odeled by applying conservation of ass and energy laws. All coponents are assued to operate under steady state conditions with fixed inlet and exit velocities and cross sectional areas. Both the heat exchangers are assued adiabatic Evaporator Mass conservation ust be satisfied in the evaporator for both aonia and butane

4 Shoaib Ahed, N Jayakrishnan, S Ganesh and Reuben George Mathew Figure 3 Evaporator y, = x, + (1) y, = x, (2) = + (3) Substituting values fro property odelling and phase diagras in the equations (1) and (2) given above, 0.55 = (4) 0.45 = (5) Using conservation of energy, Q =.h.h.h (6) Heat Exchanger 1 (Pre-Cooler) Conservation of ass will be satisfied between the evaporator and condenser/absorber. Figure 4 Heat exchanger 1 = (7) = (8) 438

5 Analysis of a Bubble Pup Driven Absorption Refrigeration Syste (Einstein-Szilard Refrigerator Variant) = (9) Applying conservation of energy.h +.h +.h =.h +.h +.h (10) Since the heat exchanger transfers heat between three streas it requires two terinal teperature differences. For the analysis, the base case is taken and the terinal teperature differences are assued to be zero Condenser/Absorber Applying conservation of ass, Figure 5 Condenser/Absorber ṁ =ṁ! (11) ṁ " =ṁ #$ (12) x %, +x %,& &= x %,' '+y %, +y %,() () (13) Since there are three fluids present in the condenser/absorber, the species equation should be stated for any two of the to copletely specify this control volue. Applying conservation of ass separately for aonia and water, x *,& &= x *,(+ (++y *,() () (14) x,& &= x,(+ (++y, +y,() () (15) Substituting values fro property odelling and phase diagras in the equations (14) and (15) given above, 0.55 &= 0.84 ( () (16) 0.45 &= 0.16 ( () (17) Using Conservation of energy, Q =.h + &.h & '.h '.h ().h () (18) 439

6 Shoaib Ahed, N Jayakrishnan, S Ganesh and Reuben George Mathew Heat Exchanger 2 Applying conservation of ass, Figure 6 Heat exchanger 2 ṁ 6 =ṁ 6 Applying conservation of energy, ṁ #$ =ṁ " (19) 67 (2 &.h &% + '.h (+ = &.h & + '.h ' (10) Since the heat exchanger transfers heat between two streas it requires a terinal teperature difference. For the analysis, the base case is taken and the terinal teperaturee difference is assued to be zero Generator 20) Applying conservation of ass, Figure 7 Generator ṁ 8 =ṁ 9 (21) ṁ #$ =ṁ " (22) ṁ # =ṁ #:+ ṁ #; (23) 440

7 Analysis of a Bubble Pup Driven Absorption Refrigeration Syste (Einstein-Szilard Refrigerator Variant) ṁ 6< = ṁ 8 + ṁ #; + ṁ " (24) x,&% &%= x,' '+ +y,() () (25) Substituting values fro property odelling and phase diagras in the equation (25) given above, Using First Law of Therodynaics, 0.44 &%= 0.16 ' () (26) Q )2 +Q =>=? =.h + '.h ' + ().h () &%.h &% (27) Taking the enthalpy values fro the Patel-Teja property odeling, we get h 1 = kj/kg, h 2 = kj/kg, h 3 = kj/kg, h 4 = 1427 kj/kg, h 5 = 1511 kj/kg h 6 = 1037 kj/kg, h 7 =h 7i = kj/kg, h 8g =1794 kj/kg, h 9 =243.5 kj/kg 4. RESULTS AND DISCUSSIONS Assuing the ass flow rate of bubble pup as kg/s and solving using the above equations, Mass Flow rates Mass flow rates & ( ' Value kg/s kg/s kg/s kg/s kg/s kg/s kg/s kg/s kg/s Substituting enthalpy values in the above therodynaic first law equations, Q = kw Q )2 + Q =>=? =3.872 kw Refrigeration Capacity = Q =0.672 kw COP = Q /Q )2 = CONCLUSION A therodynaic odel of the Einstein absorption cycle is developed to siulate its operation and investigate its feasibility liits via a careful calculation of the therodynaic properties of the ternary working fluid ixture water aonia butane with the help of the Patel Teja cubic equation of state. The therodynaic analysis has proved the viability of the proposed syste. The cycle effectively deonstrates a different approach to achieving absorption refrigeration by using a bubble pup

8 Shoaib Ahed, N Jayakrishnan, S Ganesh and Reuben George Mathew At a given syste pressure, there is a iniu evaporator teperature and a axiu condenser/absorber teperature. The axiu condenser/absorber teperature is the saturation teperature of the refrigerant at the syste pressure. In the above experient, the terinal teperature difference for the heat exchangers was assued to be zero for base case of calculation. Incorporation of suitable heat exchangers with sufficient terinal teperature differences can lead to corresponding increase in the COP. REFERENCE [1] A. Einstein, L. Szilard, US Patent No. 1,781,541, [2] Kh. Mejbri, N. Ben Ezzine, Y. Guizani, A. Bellagi. Discussion of the Feasibility of the Einstein Refrigeration Syste. International Journal of Refrigeration. 29, 2006, pp [3] Ali Benhidene, Chaouachi B, GabsiSliane.A Review of Bubble Pup Technologies. Journal of Applied Sciences. 10, 16, 2010, pp [4] Kaushik S Panara, Arat M Patel, Nikunj S patel and Jigar D Patel. Theroacoustic Refrigeration Syste Setup, International Journal of Mechanical Engineering and Technology (IJMET), 6( 11 ), 2015, pp [5] Patel N C. A new cubic equation of state for fluids and fluid ixtures. Cheical Engineering Science. 37, 3, 1982, pp [6] Ahed M. Qenawy, Abdel-Wahed F El-Dib, and Metwally M. Ghoraba. Evaluation and Perforance Study of Solar-Powered Einstein Refrigeration Cycle.Canadian Solar Buildings Conference. Montreal, August 20-24, 2004 [7] Aan Shukla, Abhishek Mishra, Devesh Shukla and Karan Chauhan, C.O.P Derivation and Therodynaic Calculation of Aonia-Water Vapor Absorption Refrigeration Syste. International Journal of Mechanical Engineering and Technology (IJMET), 6(5), 2015, pp [8] Delano A D, Design analysis of the Einstein refrigeration cycle. Ph.D. Thesis, Georgia Institute of Technology, [9] Patek, J. and J. Klofar, Siple Functions For Fast Calculations Of Selected Therodynaic Properties Of The Aonia Water Syste, International Journal of Refrigeration, 18, 4, pp [10] PongsidSrikhirin and SathaAphornratana, Investigation Of A Diffusion Absorption Refrigerator, Applied Theral Engineering, 22, pp , 442