PDF Publication Title:
Text from PDF Page: 234
7 – Discussion and Analysis ♦ The combined mode: At 60oC DHW temperature and 35/30 to 40/35oC supply/return temperatures for SH system, the COP for the prototype CO2 heat pump unit decreased by 0.8% per °C rise in the inlet water temperature. This corresponds to a drop in the COP of approx. 4 to 16%, when the inlet water temperature is increased by 5 to 20 K. ♦ The DHW mode: At 60oC DHW temperature, the COP for the proto- type CO2 heat pump decreased by 1.1% per °C rise in the inlet water temperature. This corresponds to a drop in the COP of approximately 6 to 22%, when the inlet water temperature is increased by 5 to 20 K. The Impact of Conductive Heat Transfer Inside the DHW Tank The theoretical evaluation (Section 3.3.3, Exergy Losses in the DHW Storage Tank), the experimental results (Section 5.2.1.2, Transient Temperature Gradients in a DHW Tank) and the computer simulations (Section 6.2.3, Simulation Results), demonstrated that the conductive heat transfer between the hot and cold water in the DHW tank will lead to a rise in the mean inlet water temperature for the DHW preheating gas cooler unit during the charging period. Table 7.1 presents, as an example, a rough estimate of the COP and the relative COP reduction for the proto- type CO2 heat pump unit when including the impact of the conductive heat transfer inside the DHW tank. The calculations were based on the estimated volume of the thermocline zone (Figure 6.23, Section 6.2.3.2, The Water Volume of the Thermocline Zone), Eq. (3.26) in Section 3.3.3 and the fact that the average temperature of the thermocline zone is virtually identical to the arithmetic mean of the initial water temperatures in the tank (Section 6.2.3.2). The boundary conditions were as follows: ♦ DHW tank ♦ City water ♦ Charging periods ♦ Combined mode ♦ DHW mode Standard design, 200 litres, ID 500 mm 10oC 0.5, 1, 2 and 4 hours COP = 3.89 at 35/30oC and 60oC 2 kW DHW heating capacity COP = 3.80 at 60oC 4 kW DHW heating capacity With reference to Section 6.2.3.2, the estimated volume of the thermocline zone VTC was a logarithmic function of the retention time τ in the DHW tank, i.e. VTC= [22.9·ln(τ)+30.9] ±1.5%. Consequently, the smaller the 212PDF 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)