Experimental investigation of the optimal heat rejection pressure for a transcritical CO2 heat pump water heater

Minimizing COP loss from optimal high pressure correlation for transcritical CO2 cycle

“…Kauf [8] Single-stage valve-expansion (1) SD 5.8% for p opt Liao, Zhao and Jakobsen [9] Single-stage valve-expansion (2) SD 1% for p opt Sarkar, Bhattacharyya and Gopal [10] Single-stage valve-expansion (3) N/A Sarkar, Bhattacharyya and Gopal [23] Single-stage valve-expansion (4) R 2 ¼ 0.995 for p opt Chen and Gu [11] Single-stage valve-expansion (5) (6) SD ¼ 0.94% for p opt Kim, Won and Kim [17] Single-stage valve-expansion (7) N/A Aprea and Maiorino [18] Single-stage valve-expansion (8) More accurate than Liao, Zhao and Jakobsen [9] for specific experimental p opt ; Zhang, Fan, Wang and Shen [19] Single-stage valve-expansion (9) More accurate than Liao, Zhao and Jakobsen [9] for specific experimental p opt ; Qi, He, Wang and Meng [16] Single-stage valve-expansion (10) MaxD 5% for experimental p opt ; MaxD 6% for real system COP Wang, Tuo, Cao and Xing [20] Single-stage valve-expansion (11) (12) MaxD ¼ 5.5% for experimental p opt , corresponding COP loss 1.3% Agrawal, Bhattacharyya and Sarkar [12] Two-stage valve-expansion (13) [13] Single/two-stage valve-expansion (16) N/A Ge and Tassou [15] Supermarket boost system (17) N/A Ge and Tassou [14] Supermarket boost system (18) AD ¼ 0.45%, MaxD ¼ 1.89% for p opt Sarkar [22] Single-stage ejector-expansion (19) R 2 ¼ 0.999 for p opt Elbel and Hrnjak [27] Single-stage ejector-expansion (20) N/A Xu, Chen, Tang and Zhu [24] Single-stage ejector-expansion (21) N/A Yari [21] Two-stage ejector-expansion (22) R 2 ¼ 0.9998 for p opt Fig. 2.…”

Experimental Study on the Performance of Water Source Trans-Critical CO2 Heat Pump Water Heater

“…The unique The optimal discharge pressure is one of the research hotspots in the trans-critical CO2 systems. In recent years, many theoretical analysis and experimental investigations were carried out on this topic [2][3][4][5][6][7][8][9][10][11], and some stressed on the optimal discharge pressure control [12][13][14]. However, most of these studies focused on the operating conditions when the CO2 temperature at the gas-cooler outlet is above the critical temperature.…”

Optimal fan speed and compression ratio of an air-condensed vapor-compression ammonia recycling system

“…The optimal matching of refrigerant mass flow rate and air mass flow rate is the key point (Manske et al, 2001;Zhu et al, 2013). With regard to the control strategy, variable speed compressors and condenser fans are usually used to reduce the energy-consumption (Aprea et al, 2004;Ekren et al, 2013;Qi et al, 2013;Shang et al, 2015).…”