Heat pipe as heat transfering device in geothermal heat pump systems

Geotermalne pompy ciepła są układami pobierającymi niskotemperaturowe ciepło zawarte w gruncie kosztem dostarczanej mocy elektrycznej. Dodatkowa moc pozwala na podwyższenie temperatury w obiegu na żądany poziom (np. potrzebny do przygotowania c.w.u.). Tradycyjnym rozwiązaniem pobierania odnawialnej energii z gruntu jest wykonanie pionowych odwiertów na głębokość 50-200 m i umieszczenie w nich kolektorów w formie u-rurek. Płynący w kolektorze czynnik pobiera ciepło, wiąże się to jednak z dodatkowymi kosztami energii zużywanej przez pompy obiegowe wymuszające ruch czynnika. Zastosowanie rurki ciepła zamiast tradycyjnego kolektora pozwala na obniżenie kosztów pracy układu poprzez wyeliminowanie pracy pomp obiegowych. Zasadność tego rozwiązania będzie oceniona w artykule pod względem energetycznym i ekonomicznym.Geothermal heat pumps are systems extracting low-temparture heat from the ground. Addtionall electical power is needed to raise the temperature level in heat pipe cycle (e. g. required for domestic hot water preparation). Traditional technical solution for absorbing ground energy is drilling 50-200 m deep boreholes with vertical collectors (U-shaped pipes)in them. Working fluid flows in collector pipes and draws heat from the ground, however it raises overall costs by the price of energy used by circulation pumps. Aplication of heat pipe instead of traditional vertical collector reduces overall costs of operation of heat pump system by eliminating additional pumping power for working fluid circulation. Economic and energetic rationale for applying this improved system will be discussed in this paper

Investigations of thermal-flow characteristics of minichannel evaporator of air heat pump

The results of experimental investigations of heat transfer and a friction factor in an air channel of the minichannel heat exchanger are presented. The main aim of the analysis was to examine an influence of geometrical parameters of the fin shape with two geometries on heat transfer and flow characteristics of the air channel. The test rig was designed to monitor the parameters of the airflow during cooling by the minichannel heat exchanger. The analysis was conducted with the airflow in the range of 1–5 m/s. The temperature of the evaporation in a refrigeration system was set at 288.15 K. The energy balance of the refrigeration system was carried out. A numerical model describes the airflow through a part of the heat exchanger. Numerical simulations were validated with the experimental data. Numerical methods were used to evaluate the performance of the system and possibilities to improve the fin geometry. The characteristics of the friction factor (a measure of the pressure loss in the airflow) and the Colburn j-factor (heat transfer performance) were calculated. For the maximal velocity of the airflow, the Colburn factor was equal to 0.048 and the evaporator capacity equaled 1914 W