Capillary tube length ( m )
0.6 1.2 1.8 2.4 3.0 3.6 4.2
Refrig erant m ass flo w rate ( k gs
-1)
0.03 0.04 0.05 0.06 0.07
圖 40、毛細管長度對系統冷媒質量流率的影響
Capillary tube length ( m )
0.6 1.2 1.8 2.4 3.0 3.6 4.2
Syst em COP
2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5
圖 41、毛細管長度對系統 COP 的影響
Capillary tube length ( m )
0.6 1.2 1.8 2.4 3.0 3.6 4.2
Pre ssure ( M Pa )
2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0 10.0 11.0 12.0 13.0
Compressor outlet Compressor inlet
圖 42、毛細管長度對系統高壓與低壓的影響
Capillary tube length ( m )
0.6 1.2 1.8 2.4 3.0 3.6 4.2
He at t ra ns fe r ra te and power consum pti on ( W at t )
0 2000 4000 6000 8000 10000
Gas cooler Evaporator Compressor
圖 43、毛細管長度對系統冷凝區熱傳量、蒸發區熱 傳量和壓縮機作功量的影響
圖 40-43 顯示毛細管長度對系統整體的效應，由圖 42 可看出毛細管長度 增加會使得壓降增加，促使高低壓的差距變大，而隨著低壓的下降，冷
媒的密度也會跟著降低，較低的密度便造成此後由壓縮機出來的冷媒流 率降低(圖 40) ，而冷凝區熱傳有上升的趨勢(圖 43)，但壓縮機作功並無 太多變化，因此 COP 上升(圖 41)。
4.5 改變雙套管(Gas Cooler)長度
Gas cooler tube length ( m )
2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 6.5
Re fr igeran t mass flo w rate ( k gs
-1)
0.03 0.04 0.05 0.06 0.07
圖 44、雙套管長度對系統冷媒質量流率的影響
Gas cooler tube length ( m )
2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 6.5
Sys tem COP
2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5
圖 45、雙套管長度對系統 COP 的影響
Gas cooler tube length ( m )
2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 6.5
Pr essur e ( MPa )
2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0 10.0 11.0 12.0 13.0
Compressor outlet Compressor inlet
圖 46、雙套管長度對系統高壓與低壓的影響
Gas cooler tube length ( m )
2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 6.5
He at t ra ns fe r ra te and power consum pti on ( W at t )
0 2000 4000 6000 8000 10000
Gas cooler Evaporator Compressor
圖 47、雙套管長度對系統冷凝區熱傳量、蒸發區熱 傳量和壓縮機作功量的影響
圖 44-47 顯示雙套管長度對系統整體的效應，增加套管長度，即是將熱
交換面積增加，熱傳量理所當然的提升，圖 47 顯示冷凝區的熱傳量明 顯隨著熱交換面積(套管長度)增加而上升，而冷媒在冷凝區的出口溫度 亦會隨著管長增加而降低，溫度越低則焓值越低，降低的焓值使得冷媒 進入毛細管後的壓降變小，由此便迫使原本高壓的冷媒往低處移動(圖 46)，而圖 44 顯示冷媒的流量也會略微下降，此現象可解釋為冷媒在低 壓表現出略微下降的趨勢(圖 46)，在冷媒的冷凝熱傳增加，壓縮作功幾 乎不變的情況下，系統 COP 上升(圖 45)。
五、總結
本論文研究以開發冷媒的全循環系統模擬程式為主，主要藉由模擬 改變環境溫度，環境條件對整體系統性能的影響。由模擬結果得知環境 條件的改變對系統整體性能有重要的影響，乾球溫度、濕球溫度、毛細 管長度、氣體冷卻器之雙套管長度的提升皆會使得 CO
2
熱泵系統的 COP 提升。而增加水側入口溫度或調高壓縮機轉速會使得 COP 下降。六、參考文獻
[1]. J. M. Calm, “The next generation of refrigerants – Historical review, considerations, and outlook,” International Journal of Refrigeration, Vol. 31, pp. 1123 – 1133, 2008.
[2]. P. A. Newman, “Atmospheric Chemistry and Dynamics Branch,” Private communication. GoddardSpaceFlightCenter, National Aeronautics and Space Administration (NASA), Greenbelt, MD, USA , 2007.
[3]. N. A. Rayner, P. Brohan, D. E. Parker, C. K. Folland, J. J. Kennedy, M. Vanicek, T. J.
Ansell, , S. F. B. Tett, “Improved analyses of changes and uncertainties in marine temperature measured in situ since the mid-nineteenth century: the HadSST2 dataset,” Journal of Climate, Vol. 19, pp. 446–469, 2006.
[4]. M. H. Kim, J. Pettersen, C. W.Bullard, ” Fundamental process and system design issues in CO2 vapor compression systems,” Progress in Energy and Compustion Science, Vol. 30, pp. 119-174, 2004.
[5]. G. Lorentzen, J. Pettersen, “New possibilities for non-CFC refrigeration”, In: Proc.
IIR International Symposium on Refrigeration, Energy and Environment, Trondheim, Norway. pp. 147–163, 1992.
[6]. E. A. Groll, J. H. Kim., “Review of recent advances toward transcritical CO2 cycle technology,” HVAC&R Research, Vol. 13, pp. 499-520, 2007.
[7]. Haeter A. A., ASHRAE J. 1963,47.
[8]. Chaobin Dang, Eiji Hihara, In-tube cooling heat transfer of supercritical carbon dioxide. Part 1. Experimental measurement, International Journal of Refrigeration 27 (2004) , 736–747.
[9]. C.R Zhao, P.X. Jiang, Y.W Zhang., 2011. Flow and convection heat transfer
characteristics of CO2 mixed with lubricating oil at super-critical pressures in small tube during cooling. International Journal of Refrigeration 34, 29-39.
[10]. S. M. Liao., T. S. Zhao., 2002. Measurements of Heat Transfer Coefficients From Supercritical Carbon Dioxide Flowing in Horizontal Mini/Micro Channels.
.Journal of Heat Transfer 124, 413-420.
[11]. X, Fang., Y, Xu., 2011. Modified heat transfer equation for in-tube supercritical CO2 cooling. Applied Thermal Engineering, 1-7.
[12]. N.E. Petrov, V.N. Popov, Heat transfer and hydraulic resistance with turbulent
flow in a tube of water under supercritical parameters of state, Thermal
Engineering 35 (5-6) (1988) 577-580.
[13]. X, Fang., Y, Xu., 2011. Modified heat transfer equation for in-tube supercritical CO2 cooling. Applied Thermal Engineering, 1-7.
[14]. Rin Yun , Yongchan Kim , Min Soo Kim., 2005. Flow boiling heat transfer of carbon dioxide in horizontal mini tubes. International Journal of Heat and Fluid Flow 26, 801–809.
[15]. M, Ducoulombier ., S, Colasson., J, Bonjour ., P, Haberschill., 2011. Carbon dioxide flow boiling in a single microchannel – Part II: Heat transfer. Experimental Thermal and Fluid Science 35, 597–611.
[16]. L. Cheng, G. Ribatski, L. Wojtan, J.R. Thome, New flow boiling heat transfer
model and flow pattern map for carbon dioxide evaporating inside horizontal
tubes, Int. J. Heat Mass Transfer 49 (2006) 4082–4094.
[17]. E. Hihara, S. Tanaka, Boiling heat transfer of carbon dioxide in horizontal tubes,
In: Proceedings of the 4th IIR Gustav Lorentzen Conference on Natural
Working Fluids, 2000, pp. 279–284.
[18]. Lei Gao., Tomohiro Honda., 2006. Experiments on Flow Boiling Heat Transfer of Pure CO2 and CO2-Oil Mixtures in Horizontal Smooth and Micro-Fin Tubes.
International Refrigeration and Air Conditioning Conference.
[19]. X, Zhao., P, Bansal., 2009. Experimental Investigation on Flow Boiling Heat Transfer of CO2 at Low Temperatures. Heat Transfer Engineering 30(1–2), 2–11.
[20]. Lorentzen, G., Pettersen, J., 1993. A new, efficient and environmentally benign system for car air conditioning. International Journal of Refrigeration 16, 4–12.
[21]. Lorentzen, G., 1994. Revival of carbon dioxide as a refrigerant. International Journal of Refrigeration 17, 292–300.
[22]. Lorentzen, G., 1995. The use of natural refrigerants: a complete solution to the CFC/HCFC predicament. International Journal of Refrigeration 18, 190–197.
[23]. Riffat, S.B., Alfonso, C.F., Oliveira, A.C., Reay, D.A., 1996. Natural refrigerants for refrigeration and air-conditioning systems. Appl Therm Engng, 33–41.
[24]. Neksa, P., 2002. CO2 heat pump systems. International Journal of Refrigeration 25, 421–427.
[25]. Yarral, M.G., White, S.D., Cleland, D.J., Kallu, R.D.S., Hedley, R.A., 1999.
Performance of a transcritical CO2 heat pump for simultaneous refrigeration and water heating. 20th International Congress of Refrigeration.
[26]. Stene, J., 2005. Residential CO2 heat pump system for combined space heating and hot water heating. International Journal of Refrigeration 28, 1259-1265.
[27]. Skaugen, G., Neksa, P., Pettersen, J., 2002. Simulation of trans-critical CO2 vapor compression systems. Guangdong Provincial Association of Refrigeration, 68-75.
[28]. Wang, J.F., Hihara, E., 2002. Performance comparison of heat pump water heaters using carbon dioxide and R22 as refrigerants. Guangdong Provincial Association of Refrigeration, 260-7.
[29]. Ortiz, T.M., Groll, E.A., 2002. Simulation of a 3-ton residential CO2 air conditioner.
Guangdong Provincial Association of Refrigeration, 39-46.
[30]. Pfafferott, T., Schmitz, G., 2002. Modelling and simulation of refrigeration system with the natural refrigerant CO2. Second International Modelica Conference.
[31]. Yokoyama, R., Shimizu, T., Ito, K., Takemura, K., 2007. Influence of ambient temperatures on performance of a CO2 heat pump water heating system. Energy 32, 388–398.
[32]. Sarkar, J., Bhattacharyya, S., Ramgopal, M., 2009. A transcritical CO2 heat pump for simultaneous water cooling and heating: test results and model validation.
International Journal of Energy Research 33, 100-9.
[33]. Sarkar, J., Bhattacharyya, S., Ramgopal, M., 2010. Performance of a transcritical CO2 heat pump for simultaneous water cooling and heating. International Journal of Applied Science 6, 57-63.
[34]. Cecchinato, L., Corradi, M., Fornasieri, E., Zamboni, L., 2005. Carbon dioxide as refrigerant for tap water heat pumps: A comparison with the traditional solution.
International Journal of Refrigeration 28, 1250–1258.
[35]. Yamaguchi, S., Kato, D., Saito, K., Kawai, S., 2011. Development and validation of static simulation model for CO2 heat pump. International Journal of Heat and Mass Transfer 54, 1896-1906.
[36]. Yang, J.L., Ma, Y.T., Li, M.X., Hua, J., 2010. Modeling and simulating the transcritical CO2 heat pump system. Energy 35, 4812-4818.
[37]. REFPROP, 2007. Thermodynamic properties of refrigerants and refrigerant mixtures, version 8.0, Gaithersburg, M.D. National Institute of Standards and Technology 2007.
[38]. Gnielinski V. New equations for heat and mass transfer in turbulent pipe and channel flow. Int Chem Engng 1976;16(2): 359–68.
[39]. Dang, C., Hihara, E., 2004. In-tube cooling heat transfer of supercritical carbon dioxide part 2: comparison of numerical calculation with different turbulence models. Int. J. Refrigeration 24, 748–760.
[40]. Threlkeld, J.LL., 1970, Thermal Environmental Engineering, New-York:
Prentice-Hall, Inc.
[41]. E. Hihara, S. Tanaka, Boiling heat transfer of carbon dioxide in horizontal tubes, In:
Proceedings of the 4th IIR Gustav Lorentzen Conference on Natural Working Fluids, 2000, pp. 279–284.
[42]. McAdams WH, Woods WK, Bryan RL. Vaporization inside horizontal tubes-II-Benzene-oil mixtures. Trans ASME 1942;64:93–200.
[43]. Neeraj Agrawal1, Souvik Bhattacharyya, Prasant Nanda., 2011. Flow characteristics of capillary tube with CO2 transcritical refrigerant using new viscosity models for homogeneous two-phase flow. International Journal of Low-Carbon Technologies 6, 243–248.
[44]. Lin S, Kwok CCK, Li RY, et al. Local friction pressure drop during vaporization of R-12 through capillary tubes. Int J Multiphase Flow 1991;17:95–102.