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Journal ofScience & Technology 100 (2014) 031-035 Study on Power Consumption and Energy Performance of Split-Type Air-Conditioners Hoang-Luong PHAM^\ Shogo TOKURA^, Viet-D ung NGUYEN', Nguyen-An NGUYEN^ Ngoc-Anh LAI' 'Hanoi Umversity of Science and Technology, No 1, Dai Co Viet Str, Hai Bo Trung, Ha Noi, ^Heat Pump and Thermal Storage Technology Center Tokyo, Japan Received: May 16, 2013; accepted: April 22 2014 VietNam Abstract An experimental study was earned out to compare energy performance of a non-inverter Air-Conditioner (AC) and that of an inverter AC having the same rated cooling capacity of 12000 BTU/h Under different cooling part load values of 25% 50% 75% and 91% it is found that compared to the non-inverter AC, the inverter one can save from 10%, to 52%, of power consumption Coefficient of pertormance (COP) of the inverter AC and that of the non-inverter one were also estimated to be in the range of 3.1 to 5.2 and 2.3 to 2.9 respectively Keywords- Split-type Air-conditioners, Power consumptions, COP, experimental study Introduction Coefficient of perfonnance (COP) is normally used to evaluate energy efficiency for AC, (Shao et al., 2004; Zhu, 2006; Yu and Chan, 2007) Pham et al addressed that the COP of a 12000BTU/h inverter AC consumes from % to 26.9% less electricity compared to a non-inverter AC having the same rated capacity (Pham et al., 2011a) Finally, Yokoyama found that under part load condition, power consumption of a 9000 BTU/h inverter AC is 8% to 10% lower than that of a non-inverter AC of the same rated capacity (Yokoyama, 2011) Based upon power consumption and COP concepts, this study focuses on a comprehensive comparison in energy performance of a non-inverter AC and that of mverter-AC having the same rated cooling capacity of 12000 BTU/h under Hanoi climate conditions Experimental Set-Up and Calculation Method 2.1 Experimental set-up The set-up used for this study consists of two identical testing rooms each having a dimension of 4.9 m width, 3.0 m length and 3,2 m height, and being insulated by polystyrene panels (Fig I) Major details of the set-up were described elsewhere (Pham et al., 20 II a) For the current study, some improvements were made i.e; i) Use of HF5 Rotiomc sensors with high accuracy for temperature and • Corresponding author: Tel (+844) 3868 0406, Email: luong.phainhoaiig@hust.edu.vn humidity measurement, ii) Better insulation and sealing of the floor and ceiling of the testing rooms, iii) Use of PLC controllers for artificial heat load devices with different setting modes, and iv) Use of a ceiling fans for better air circulation m the testing rooms (Pham, etal,, 20IIb), Before the expenmental work was conducted, a number of tests for heat transfer through the wail of the rooms were conducted Based upon the experimental data, the heat transfer through the wall of the rooms, Qioss, can be calculated as below For the room equipped with the inverter AC Qbss= 41 554 (TouB,d=-T,ns,de) + 0.0289, W (I) For the room equipped with the non-inverter AC QloBB = 4I.i68(Touts,de-r,nB,de) + 3 , W (2) where Toutside and I'msidc are outside and inside temperatures of the rooms, respectively By setting the room temperature of 20 "C, the afr leakage of the room with the inverter AC and that with the non-mverter AC were estimated to be 36 g water per hour and 28 g water per hour, respectively These data show that the testing rooms are in good airtight and insulation conditions 2.2 Calculation of COP as: COP of an AC in each testing room is defined COP-Qo/P (3) Journal ofScience & Technology 100 (2014) 031-03S Fig A schematic diagram of the experimental set-up 1200 • m - E c 600 % 400 200 • • ^^_ij_^ •• * I ^ i " * 2B.0 J^ A ^ ^ lL*ffA ** - A ^ -&-*- "^ 29.0 30.0 31.0 32 Outside temperature (oC) 33 34,0 Fig Effect of the outside temperature on power consumption of the inverter AC under part load ratios of o 91%, • 75%, A 50%, and 25% ( ), and that of the non-inverter AC under part load ratios of • 91%, • 75%, A 50%, and • 25% (—) Where Qo is the cooling capacity of AC which equals to the sum of heat transfeired through the wall of the room, heat created by the circulation fan, and heat generated by the artificial heat load device P is the power consumption by AC which is measured by HIOKI measurement on an every minute interval Before each experimental run, the AC cooling load can be fixed by keeping tmchanged the inside temperature of the rooms at around 27 "C and conttolling the electiic power of the artificial heat load device with a pulse width modulation method (Pham et al., 201 ia), AC part load ratio is ultimately defined as ratio of the AC preset cooling load to its rated cooling capacity Results and Discussions 3.1 Effect of the Outside Temperature on Power Consumption of the AC Table presents the experimental results on power consumptions of the inverter AC and that of the non-inverter one under different cooling part load ratios and at different outside temperatures measured from July to September 2011 At each given temperature, we average all measured values for the cases having the given temperature plus and minus 0.5K The relation between power consumption and outside temperature under different cooling part load ratios is shown in Fig 2, As can be seen for both cases of AC tiiat: i) At a given part load ratio, the higher the outside temperature, the higher the power consumption of AC for both cases, and ii) At the same outside temperature, the higher the part load ratio, the higher the power consumption These observations agree well with the theory Journal ofScience & Technology 100 (2014) 031-035 Table Power consumption of ihe two AC Part load ratio 25% 50% 75% 91% To.i,d.,°C Pin.m«(l),W P no „.m, (2), W (1)-P) ((l)-(2))/(2) 28 30 32 34 28 30 32 34 28 30 32 34 28 30 32 34 150 170 190 210 312 343 373 403 703 757 812 866 311 321 332 342 570 592 614 636 837 887 936 986 161 151 142 132 258 250 241 233 134 129 124 120 111 130 148 167 52% 47% 43% 39% 45% 42% 39% 37% 16% 15% 13% 12% 10% 11% 1004 1115 1018 1148 1033 1181 1047 1214 13%, 14% Table COP of the two AC Part load ratio 25% 50% 75% 91% T„,.,d.eC) 28 30 32 34 28 30 32 34 28 30 32 34 28 30 32 34 COPi.,„„(l) COPn=n-in,m., (2) (I)-(2) ((l)-(2))/(2) 4.78 34 2.44 4.72 2.50 2.22 4.67 2.67 2.01 4.62 2.83 1.79 5.17 2.85 2.32 4.94 2.85 2.09 4.71 2.86 1.85 4.48 2.87 1.61 3.54 2.95 0.60 3.43 2.89 55 3.32 2.83 0.49 3.22 2.77 0.44 3.10 2.85 25 3.08 2.81 27 3.07 2.78 0.29 3.05 2.74 0.31 104% 89% 75% 63% 82% 73% 65% 56% 20% 19% 17% 16% 9% 10% 11% 11% Comparison m power consumption of the two AC is illustiated in Fig From this Fig., one can find that the higher part load ratio, the lower the relative power consumption difference Furthermore, the lower the outside temperature, the more inclined the relation between the relative power consumption difference and part load ratios It should be noticed that this ttend is different from that stated earlier by Pham et al (2011a) This could be intepreted that in the previous work, the AC temperatures were fixed while in this study, the rooms temperatures were kept unchanged 3.2 Effect of the Outside Temperature on COP of the AC Table presents the experimental results on COP of both non-inverter and inverter AC under different part load ratios and at different outside Journal of Science & Technology 100 (2014) 031-035 temperatures Relative difference in COP of the nonmverter and inverter ACs is also given in Table which decreases quickly with an increase m the outside temperature Fig Effect of the part load ratio on relative power consumption difference between the inverter and nonmverter ACs at various outside temperatures of o34 "C, • 32 "C, A 30 "C, and 28 "C Relation between the relative COP difference and part load ratio at different outside temperatures is presented m Fig 4, The Fig, shows that the higher part load ratio, the lower the relative COP difference Furthermore, the lower the outside temperature, the more inclined the relation hetween the relative COP difference and part load ratio Again, this tiend is different from that obtamed from the previous work conducted by Pham et al., (2011a) The reason for such difference is similar to that already addressed when one examines the outside temperature on power consumption of the AC performance of a non-inverter AC and an inverter AC having the same rated cooling capacity of 12000 BTU/h was conducted Under part load ratios from 25%i to % and: with outside temperatures variation from 28 °C to 34 "C, power consumption of inverter AC and noninverter AC is found to be from 150 W t o I047Wand from 311 W to 1214 W, respectively The power consumption increases with an increase in part load ratio and outside temperature The relative power consumption of non-inverter and inverter ACs is seen to decrease from 52%) down to 10%) wtth increase in part load ratio from 25%) up to 9I%o that corresponds with increase m outside temperature from 28 °C to 34 "C Under the same operating conditions, COP of the non-inverter AC and inverter one was found to be in the order of 2.3 to 2.9 and 3.1 to 2, respectively, The relative difference m COP of the inverter and non-inverter AC is observed to decrease from 104% down to 9% with increase in part load ratio and with increase in outside temperature difference The results obtained from this work have shown a suitable application of inverter AC under Hanoi's climate conditions that would contiibute to the reduction of electiicity consumption and thus CO2 emission from the residential sector in Hanoi, Vietnam Acknowledgements The authors gratefully acknowledge the Heat Pump and Thermal Storage Technology Center of Japan for their financial support for this study Laboratory facilities provided by the Hanoi University of Science and Technology for this research work are also highly appreciated References [I] Pham H L,, Nguyen V, D,, Nguyen N A., Lai N A,, Tokura S., Nakamura S., Development of energy performance comparison method for residential electric appliances - application to air conditioners Proceedings of the IO*IEA Heat Pump Conference, Tokyo, Japan, pp 13, 201 la [2] Pham H L,, Tokura S., Nguyen V, D,, Nguyen N, A,, Lai N A., Improvement of methodology for energy performance estimate of small-scale air conditioners in Vietnam, The First Project Progress Report, submitted to the Heat Pump and Thermal Storage Technology Center of Japan, U b [3] Shao S, Shi W, Li X„ Chen H„ Perfonnance representation of variable-speed compressor for inverter afr conditioners based on experimental data, International Joumal of Refrigeration, Vol, Part load ratio (%) Fig Effect of the part load ratio on relative COP difference of the non-inverter AC and mverter one at various outside temperatures of o 34 "C, • 32 "C, A 30 "C and 28 °C Conclusions By carrying out an expenmental study using "two identical testing rooms" set-up with appropriate improvements in room insulation, temperature measurement and contiol, companson in energy Journal ofScience & Technology 100 (2014) 031-035 27(2004)805-815 [4] Yokoyama K., Methodology for estimate of Annual Performance Factor (APF) and its application into Japanese Conditions, Proceedings of the Vietnam-Japan Workshop on Methodology for estimate of Annual Performance Factor (APF) for Air Conditioners in Vietnam, Hanoi University of Science and Technology, Vietnam, 2011 [5] Yu F.W., Chan K.T., Part load perfonnance of air-cooled centiifugal chillers with variable speed condenser fan control Building and Envfronment, 42 (2007) 3816-3829 [6] Zhu H., Impact of the Variable Refrigerant Volume Air Conditioning System on Building Energy Efficiency, HVAC Technologies for Energy Efficiency, Proceedings of the 6"' International Conference for Enhanced Building Operations, Shenzhen, China, Vol, IV-I-3, 2006
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