Scholarly article on topic 'Experimental Evaluation Mechanical Performance of the Compressor with Mixed Refrigerants R-290 and R-600a'

Experimental Evaluation Mechanical Performance of the Compressor with Mixed Refrigerants R-290 and R-600a Academic research paper on "Materials engineering"

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{"Mixed Refrigirents" / VCRS / "Data Aquitisation system" / Compressor / R290/R600a}

Abstract of research paper on Materials engineering, author of scientific article — Tejaswi Saran Pilla, Pranay Kumar Goud Sunkari, Sai Laahiri Padmanabhuni, Sachu Sasidharan Nair, Raja Sekhar Dondapati

Abstract Mixed refrigerant systems are reported to be thermally efficient. However, the mechanical input required by the compressor is not investigated in the literature. Hence, in the present work, two refrigerants are chosen (R-290 and R-600a) to evaluate the mechanical performance of compressor of domestic refrigerators. The refrigeration cycle consists of four major processes. The isentropic compression in the compressor, isobaric heat rejection in the condenser, isenthalpic reduction in pressure and isobaric heat addition in the evaporator. The present work aims at investigation of mechanical performance of compressor with mixed refrigerants (R-290 and R-600a). The boiling point of the each of the refrigerant is different and hence the specific volume occupied by each is different. This in turn affects the work input required. Hence, the present work is aimed at evaluating the compressor performance with mixed refrigerants. The temperature distribution during the cycle operation process is estimated. This turn enables the effective design of the compressors for domestic refrigeration systems for effective operation.

Academic research paper on topic "Experimental Evaluation Mechanical Performance of the Compressor with Mixed Refrigerants R-290 and R-600a"

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Energy Procedia 109 (2017) 113 - 121

International Conference on Recent Advancement in Air Conditioning and Refrigeration

RAAR 2016

Experimental evaluation Mechanical performance of the compressor with mixed refrigerants R-290 and R-600a

Tejaswi Saran Pillaa, Pranay Kumar Goud Sunkaria, Sai Laahiri Padmanabhunia, Sachu Sasidharan Naira, Raja Sekhar Dondapatia*,

aSchool of Mechanical Engineering, Lovely Professional University, Phagwara 144402, India,

Abstract

Mixed refrigerant systems are reported to be thermally efficient. However, the mechanical input required by the compressor is not investigated in the literature. Hence, in the present work, two refrigerants are chosen (R-290 and R-600a) to evaluate the mechanical performance of compressor of domestic refrigerators. The refrigeration cycle consists of four major processes. The isentropic compression in the compressor, isobaric heat rejection in the condenser, isenthalpic reduction in pressure and isobaric heat addition in the evaporator. The present work aims at investigation of mechanical performance of compressor with mixed refrigerants (R-290 and R-600a). The boiling point of the each of the refrigerant is different and hence the specific volume occupied by each is different. This in turn affects the work input required. Hence, the present work is aimed at evaluating the compressor performance with mixed refrigerants. The temperature distribution during the cycle operation process is estimated. This turn enables the effective design of the compressors for domestic refrigeration systems for effective operation.

© 2017 The Authors.Publishedby ElsevierLtd. This is an open access article under the CC BY-NC-ND license

(http://creativecommons.Org/licenses/by-nc-nd/4.0/).

Peer-review under responsibility of the organizing committee of RAAR 2016.

Keywords: Mixed Refrigirents; VCRS;Data Aquitisation system;Compressor;R290/R600a;

1. Introduction;

Refrigeration and Air conditioning supplies are broadly and imperatively utilized as a part of numerous fields. Both Choloro Flouro Carons (CFCs) and Hydro-Chloro Flouro Carbons (HCFCs) were regularly utilized as the refrigerant as a part of the most recent couple of decades. Shockingly, these sorts of refrigerant truly drain the ozone layer and add to the nursery impact.

Corresponding author: Tel: +91-842-747-4117. E-mail address: drsekhar@ieee.org

1876-6102 © 2017 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

Peer-review under responsibility of the organizing committee of RAAR 2016. doi:10.1016/j.egypro.2017.03.065

Nomenclature

COP Coefficient of performance Pi Suction Pressure (bars)

CFC Chlorofluorocarbons P2 Discharge Pressure (bars)

HC Hydrocarbons P3 Condensation Pressure (bars)

HFC Hydrofluorocarbons P4 Evaporator Pressure (bars)

hlef Enthalpy of saturated vapour at the exit of evaporator (kJ/kg) Ti Suction Temperature (oC)

h4ef Enthalpy of saturated liquid at the exit of condenser (kJ/kg) T2 Discharge Temperature (oC)

mr Mass flow rate of the refrigerant (kg/sec) T3 Condensation Temperature (oC)

M1 Molecular weight of R290 (g/mol) T4 Evaporator Temperature (oC)

M2 Molecular weight of R600a (g/mol) Wc Isentropic work done (kJ/kg)

Qe Refrigeration capacity, kW Wc Power Consumption (kW)

R290 Propane

R600a Isobutane

The aim is to investigate the mechanical performance of compressor with mixed refrigerants (R-290 and R-600a)

[1]. The experiment works on the bases of thermal transfer of heat in vapour compression refrigeration system. This results can be used for future research works and can be used in the compressor for the maximum refrigeration effect. This results in optimize the R290/R600a mixture as usable volumetric concentration in domestic refrigerating system as refrigerant. A reasonable refrigerant not just needs to give worthy natural properties, yet should likewise meet the accompanying prerequisites which are critical for its utilization 1. No combustibility; 2. Low danger; 3. High compound and warm dependability; 4. Reasonable physical and thermodynamic properties; 5. Similarity with materials; 6. Miscibility with other refrigerant. Most imperative as the primary choice standard is the thermodynamic properties, which choose whether a substance is appropriate as a refrigerant in a specific temperature extend or not

[2]. Be that as it may, the refrigerant most usually considered as the future substitute for CFC12 in household hardware was HFC 134a. Numerous computations taking into account straightforward Rankine cycle models, in any case, have presumed that HFC134a is less vitality productive than CFC123s. These cases were affirmed by trial results which demonstrated efficiencies for HFC134a which were 4-10% less than those for CFC12 [3]. Test execution attributes of household fridges working with propane/iso-butane blend were assessed by numerous specialists reported that the propane/ iso-butane blend at half mass division of propane yields higher COP, lower charge and lower compressor shell temperature when contrasted with R12.They affirmed that vitality investment funds of up to 6% were accomplished with a mix of 70% propane and 30% n-butane contrasted with R12This expressed that R134a spillage and administration emanations yield 15% expansion in Total Equivalent Warming Impact (TEWI) [4]. The investigations have demonstrated that, even without outline changes or framework streamlining, a cooler in which propane has been substituted for R12 is equipped for comparative execution with a lower charge. The blast dangers are little and the flame dangers are comparable, yet huge in terms of smoke and oil blazing. Propane introduces an appealing other option to current CFCs in little frameworks, for example, the residential cooler, given right specialized application for operational and wellbeing elements. [5]. In this experiment, we intend to run the refrigeration rig in our laboratory using blends of refrigerants, which are R600A and R290 at different proportions. A perfect vapor-pressure refrigeration framework is utilized for the execution investigation of option new refrigerant blends as substitutes for CFC12, HFC134a, and CFC22. Considering the examination of execution coefficients (COP) and weight proportions of the tried refrigerants furthermore the primary ecological effects of ozone layer consumption and worldwide warming, refrigerant mixes of HC290/HC600a (40/60 by wt.%) furthermore, HC290/HC1270 (20/80 by wt.%) are observed to be the most reasonable choices among refrigerants tried for R12 and R22 separately [6]. A minimized VCC model was composed and created. Broad parametric studies were conveyed out to better comprehend framework attributes under changing working conditions. Moving limit models were created for recuperator and condenser to discover the impact of changing the working condition on this warmth exchanger's execution. The recuperator model could foresee the sum of super-warmth and sub-cooled degrees added to the refrigerant at various working focuses. The model is combined with other part models and

coordinated into a cycle-level model [7]. In this work a PC code for the temperamental state investigation of a little hermetic responding compressor for local refrigeration was introduced. The model was capable to assess the refrigerant mass stream rate, the electric power includes, the warmth stream rates and the temperatures inside the hermetic unit, the trademark parameters' pattern amid the pressure cycle and the proficiency of the pressure cycle and of the hermetic unit. The model can be effectively adjusted to various compressor geometry and diverse agent fluids; therefore, it can be a valuable apparatus for the examination, the configuration and the improvement of hermetic responding compressors [8]. We have concluded the basis of our experiment when we were introduced to a fact that a refrigerant blend can show comparably higher COP in a refrigeration system than that of a single refrigeration system. Our exploration shows that propane/isobutene blends can be utilized as a 'drop in' trade for R12 in vapor-pressure refrigeration frameworks, and can accomplish large amounts of COP. The compressor utilized as a part of our trials was a standard hermetic unit, and the producer's greasing up oil charge was held all through. Following a few hundred hours' operation, utilizing an assortment of refrigerants, no issues have been experienced with the compressor and no debasement of the greasing up oil could be distinguished. Filling or releasing of hydrocarbon [9]. The COP exploratory estimations demonstrate that substituting an unadulterated HCFC liquid, for example, R22 is disadvantageous since the distinctive substitution liquids give a less agreeable rendering because of their specific thermo-physical properties in a framework estimated for the given unique liquid. This ought to prompt a reflection on the utilization of option liquids in existing frameworks [10]. The aim is to investigate the mechanical performance of compressor with mixed refrigerants (R-290 and R-600a). The boiling point of the each of the refrigerant is different and hence the specific volume occupied by each is different. This in turn affects the work input required. Hence, the present work is aimed at evaluating the compressor performance with mixed refrigerants. The temperature distribution during the cycle operation process is estimated. This turn enables the effective design of the compressors for domestic refrigeration systems for effective operation. Depending on the type of liquid produced mixing of refrigerants take place. The chemical, thermal, thermo-physical and environment properties of the new mixture varies from that of the initial pure refrigerants mixed.

This experiment is subjected to the mixing of flammable hydrocarbons R290/R600a at different volume concentrations. These hydrocarbons are naturally flammable but still can mix them and cannot flu up. This is due to maintain optimum condensation and evaporation temperature. This mixture is based on the study and research. This involves the miscibility properties of the refrigerant, the boiling point and the freezing point variation. According to research review, the COP of mixed refrigerant is high, it has more refrigeration effect and depending on the mixture percentage more or less power consumption. From the experimentation work we understand to find the optimum volume concentration of the hydrocarbon mixture that produces higher COP, better refrigeration effect, lower power consumption, better performance by the compressor and also show that this mixture can be commercialized and used in our domestic refrigerators.

2. Research Methodology

2.1 Experimental set up

Our test rig shown in figure1 mainly comprises of four major components they are compressor, condenser, expansion device and evaporator as in basic VCRS. We brought components individually and assembled as a domestic refrigerator test rig in which mixture of R290/R600a is used as refrigerant.

Table1 shows the specifications of our compressor. It is a single cylinder hermetic reciprocating compressor designed and manufactured by Godrej & Boyce. Co. Ltd. It is designed for only R134a. This type of compressors currently using in almost every domestic refrigerator. There is no compressor designed for R290/R600a so that we did our experiments in this compressor.

Figure 1 A) Experimental Test Rig of Domestic Refrigerator B) Schematic Diagram of the experimental Setup

Table 1 Specifications of Compressor

Compressor type Hermetic reciprocating compressor

Compressor model POWER COOL COMP R134a G1-1+CAPCT

Size (dimensions) 20.1cm X 16.4cm X 17.5cm

Cooling capacity 120 watts or 410 Btu/hr

Frequency 50 Hz

Condenser is wire and tube type and having serpentine shape. Heat is rejected to the air by natural convection. Next roll-bond evaporator is used. It is a box type heat exchanger made up aluminium. It has unique design flexibility and compatible to R290/R600a. Capillary tube type expansion device is used.

For measuring pressures, Bourdon pressure gauge is used. There are four pressure gauges for measuring pressure in suction and discharge of compressor, condensing and evaporative pressures. For measuring temperature at each point four DS18B20 temperature sensors are used. Table2 shows the specifications of the temperature sensors.

Table 2 Specifications of DS18B20 temperature sensor

Temperature range Resolution Accuracy Power usage

-55 to 1250C (-670F to +2570F) 9-12 bit ±0.5°C 3 V to 5.5 V

2.2 Test procedure

First, the capillary tube and the whole components of the test rig are to be evacuated using the vacuum pump so that no other gases and impurities may present and reacts with the refrigerants. Once the system is evacuated then the suction line of the compressor is attached with the valve of a refrigerant cylinder using the dual pressure gauges. By measuring the back pressures inside the compressor we can fill the required amount. While charging the mixed refrigerant one should note the densities and pressures of the refrigerants. The refrigerant with low pressure should be charged first, hence the mixing of refrigerants takes properly. In this experiment, R600a and R290 has pressures

of 3.64 Mpa and 4.25 Mpa, so we charged R600a first and simultaneously the R290. Once the experiment is started the temperatures at the outlets of each component (namely, evaporator, compressor, condenser and expansion devices) are measured by using the DS18B20 sensor assisted with the Data Acquisition System. The pressures are noted by using the pressure gauges.

Table3 show the experimental readings of pressures at each significant point were taken by using pressure gauges and temperatures at suction and discharge of compressor, condenser and evaporator were taken by using temperature sensors associated with DAQ.

Table 3 Experimental data

R290/ R600a Pi Ti (oC) P2 T2 (oC) PH" II P T3=Tc (oC) P4=Pe T4=Te (oC)

90/10 0.09 18.9 11.17 55.44 10.8 32.9 0.09 -23

80/20 0.49 17.3 15.69 46.94 15.2 32.4 0.29 -20.1

70/30 0.49 16.7 12.74 46.88 12.3 34.7 0.98 -18.6

60/40 0.09 16.5 8.53 46.69 8.04 32.3 0.39 -20.4

50/50 0.29 20.9 9.61 51.31 8.9 29.6 0.19 -20.2

40/60 0.19 17.4 7.06 52.63 5.8 30.9 0.34 -24.2

30/70 0.29 19.8 7.64 52.38 7.06 32 0.28 -20.4

20/80 0.19 20.2 6.66 52.13 5.98 31.7 0.26 -20

10/90 0.14 24.2 5.8 47.56 5.09 28 0.29 -13.6

2.3 Solution Methodology

For any measured or observed evaporator and condenser pressures, the performance parameters of the reciprocating compressor are:

1. Mass flow rate of the refrigerant (mr) in kg/sec or gm/sec

2. Power consumption of the compressor (Wc) in kW or W

3. Co-efficient of performance (COP)

4. Discharge temperature (Td) in Kelvin K

For calculating performance parameters, required sub parameters are:

1. Enthalpy of saturated vapour at the exit of evaporator, h1ef kJ/kg

2. Enthalpy of saturated liquid at the exit of condenser, h4ef kJ/kg

3. Isentropic index of compression, y = 1.304

4. Refrigeration capacity, Qe= 0.12 kW= 120 W

5. Evaporator temperature, Te in Kelvin (K)

6. Evaporator pressure, Pe in bars

7. Condenser temperature, Te in Kelvin (K)

8. Condenser pressure, Pc in bars

9. Molecular weight of R290, Mj= 44.096 g/mol

10. Molecular weight of R600a, M2= 58.122 g/mol

11. Gas constant, R kJ/kg. K

Mass flow rate (mr) =

refrigeration capacity

kg_or_gm

refrigeration effect hef - h4ef sec sec

Work done by the compressor (wc) = R x T x

rzi ( p y

V pe J

Power consumption (Wc) = wc x mr = kW orW

Co-efficient of performance (COP) = 0e-

Second law efficiency (n||) = COP

( t_T ^

V 1e y

3. Results and Discussions

Table4 shows the performance results of the compressor. All are calculated using formulae except discharge temperature as it is directly measured by using temperature sensor which was connected at the discharge port of the compressor.

Table 4 Performance data of the compressor

m1/m2 mr wc Wc' COP Second law Carnot Td

(kg/sec) (kJ/kg) (kW) efficiency COP (K)

90/10 0.0003913 205.7 0.08 1.49 0.333 4.47 328.44

80/20 0.000393 390.4 0.15 0.78 0.162 4.82 319.94

70/30 0.0004012 282.4 0.11 1.05 0.221 4.77 319.88

60/40 0.000395 145.6 0.05 2.08 0.434 4.79 319.69

50/50 0.000371 258.5 0.09 1.25 0.246 5.07 324.31

40/60 0.0004019 170.5 0.06 1.75 0.387 4.51 325.63

30/70 0.0003910 181.6 0.071 1.68 0.448 3.76 325.38

20/80 0.00039 180.7 0.07 1.701 0.347 4.89 325.13

10/90 0.000373 161.6 0.06 1.98 0.319 6.29 320.56

Various performance graphs are obtained by plotting between refrigerant composition and performance parameters.

Figure2 shows the graph plotted between refrigerant composition and mass flow rate of refrigerant, the graph shows that 40% of R290 and 60% of R600a having the highest mass flow rate while 50% of R290 and 50% of R600a having the lowest. To enhance better cooling rate for the motor windings, mass flow rate of the refrigerant should be more or else motor windings get heated and there will be a chance of short circuit. Figure3 shows the graph plotted between refrigerant composition and Power consumption, the graph shows 60% of R290 and 40% of R600a composition consumes low power and while 80% of R290 and 20% of R600a composition consumes more.

For low capacity refrigeration there is a chance to use small compressor by using 10% of R290 and 90% of R600a composition which will reduce the power consumption as shown in the figure. It has low mass flow rate and low mass will accumulate in the compressor and hence it is better suited to low capacity compressor. It also consumes low power and hence energy will save. Figure4 shows the graph plotted between refrigerant composition and Experimental COP, the graph shows 60% of R290 and 40% of R600a has the maximum COP while 80% of R290 and 20% of R600a composition has minimum. Figure5 shows the graph plotted between refrigerant composition and Carnot COP, the graph shows 10% of R290 and 90% of R600a composition has highest Carnot COP while 30% of R290 and 70% of R600a composition having low. Figure6 shows the graph between refrigerant composition and discharge temperature. Discharge temperature is the temperature at outlet of the compressor. It shows effect on life of the compressor. 60% of R290 and 40% of R600a has low discharge temperature w.r.t desired outlet temperature and hence it again proves it is better composition.

Figure 2 Refrigerant composition vs Mass flow rate

Figure 3 Refrigerant composition vs Power Consumption

Refrigerant composition Vs Experimental COP

Kef ri gérant composition (K29D+R<500a)

Figure 4 Refrigerant composition Vs Experimental COP

Refrigerant composition Vs Carnot COP

3.5 -1-1-1-1-1-1-1-

Refrigerant composition {R29Û-*-R600a)

Figure 5 Refrigerant composition vs Carnot COP

Réfrigéra m Composition Vs Discharge Temperature

318 ---,-,-,-,-,-,-,-,

% -fc, -St

vo v<? v<? so \> ~ï>

Refrigf raniiompo-sinon rR290~R600a)

Figure 6 Refrigerant composition vs Discharge Temperature

For low capacity compressor using 10% of R290 and 90% of R600a composition is reliable since it is having low discharge temperature. Discharge temperature is the parameter which decides life time of the compressor. If discharge temperature is low, then the time taken for decrease of temperature from superheated state to saturated state is also less. Then the cooling effect is achieved in less time.

4. Conclusion

The present work concludes that 60% of R290 and 40% of R600a composition has better performance in all parameters such as mass flow rate, power consumption, experimental COP, Carnot COP and discharge temperature.

Small compressors can be use instead of usual one to obtain equal performances by using 10% of R290 and 90% of R600a composition. Because it also has better performance parameters along with 60%of R290 and 40% of R600a composition and also it consumes low power hence energy will save. It has highest Carnot COP i.e., almost equals to ideal cycle for some extent.

References

[1] Lee, Y. S., & Su, C. C. (2002). Experimental studies of isobutane (R600a) as the refrigerant in domestic refrigeration system, 22, 507-519.

[2] Preisegger, E., & Henrici, R. (1992). Refrigerant 134a: The first step into a new age of refrigerants Le R134a: Le premier d ' une nouvelle srrie de frigorigrnes, (June).

[3] Radermacher, R., & Kim, K. (1996). Domestic refrigerators: recent developments R6frig6rateurs domestiques: mises au point r6centes, 19(1).

[4] Fatouh, M., & Kafafy, M. El. (2006). Experimental evaluation of a domestic refrigerator working with LPG, 26, 1593-1603.

[5] Road, B., & Polytechnic, S. B. (1991). The use of propane in domestic refrigerators Utilisation du propane dans les r6frigerateurs domestiques, 1(2), 95-100.

[6] Dalkilic, A. S., & Wongwises, S. (2010). A performance comparison of vapour-compression refrigeration system using various alternative refrigerants. International Communications in Heat and Mass Transfer, 37(9), 1340-1349.

[7] Alzoubi, M. A., & Zhang, T. (2015). Characterization of Energy Efficient Vapor Compression Cycle Prototype with a Linear Compressor. Energy Procedia, 75(2), 3253-3258.

[8] Longo, G. A., & Gasparella, A. (2003). Unsteady state analysis of the compression cycle of a hermetic reciprocating compressor ' compression en re ' gime transitoire d ' un Analyse du cycle a ' tique a ' piston compresseur herme, 26, 681-689.

[9] Richardson, R. N., & Butterworth, J. S. (1994). vapour-compression refrigeration system p r o p a, (July 1993).

[10] Rocca, V. La, & Panno, G. (2011). Experimental performance evaluation of a vapour compression refrigerating plant when replacing R22 with alternative refrigerants. Applied Energy, 88(8), 2809-2815.