PDF Publication Title:
Text from PDF Page: 177
The relatively high mass flux led to turbulent flow and excellent heat transfer efficiency for the space heating gas cooler in the combined mode and the SH mode (hi~2800 to 7300 W/(m2K)). Owing to the considerable temperature difference in the hot water circuit, the water flow rate for the DHW gas cooler units was about 5 to 30 times lower than that of the space heating gas cooler at optimum high-side pressure. During operation in the combined mode, low Reynolds numbers in most of the experiments resulted in laminar flow and poor heat transfer (hi~700 to 850 W/(m2K)). In the DHW mode, however, the water flow rate was roughly twice as high as in the combined mode, which led to turbulent flow and a conside- rable rise in the convective heat transfer coefficient (hi~2000 to 3300 W/(m2K)). During operation in the combined mode, the water-side heat transfer resis- tance for the DHW gas cooler units constituted about 80 to 85% of the total heat transfer resistance. Hence, the presumed 25% drop in the con- vective heat transfer coefficient for the CO2 caused by the 6 to 9% oil con- centration in the flow, had only a marginal influence on the overall heat transfer coefficient. For the space heating gas cooler as well as for the DHW gas cooler units during operation in the DHW mode, the presence of oil reduced the U-value by roughly 10 to 15%. Pressure Drop The pressure drop for the supercritical CO2 was measured for each gas cooler unit. The total pressure drop for the tripartite gas cooler in the com- bined mode, the DHW mode and the SH mode ranged from about 130−200 kPa, 95−155 kPa and 85−100 kPa, respectively. Figures 5.49 to 5.51 show the mean pressure drop gradients in kPa/m for the gas cooler units in the three operating modes. Since the mass flow rate of the supercritical CO2 and the lubricant was virtually constant (1.42 kg/min ±2%), the differences and variations in the mean pressure drop gradients for the three gas cooler units were merely a result of the considerable impact of the temperature and the high-side pressure on the density and the dynamic viscosity of the supercritical CO2. With reference to Figures A4 and A5 in Appendix A1.6, Heat Exchanger Performance, both the density and the dynamic viscosity drop off at increasing fluid temperature and rise when the high-side pressure is increased. 5 – Experimental Results 155PDF Image | Residential CO2 Heat Pump System for Combined
PDF Search Title:
Residential CO2 Heat Pump System for CombinedOriginal File Name Searched:
20559406.pdfDIY PDF Search: Google It | Yahoo | Bing
CO2 Organic Rankine Cycle Experimenter Platform The supercritical CO2 phase change system is both a heat pump and organic rankine cycle which can be used for those purposes and as a supercritical extractor for advanced subcritical and supercritical extraction technology. Uses include producing nanoparticles, precious metal CO2 extraction, lithium battery recycling, and other applications... More Info
Heat Pumps CO2 ORC Heat Pump System Platform More Info
CONTACT TEL: 608-238-6001 Email: greg@infinityturbine.com (Standard Web Page)