Naslov
Experimental Investigation of Parameter Driven Defrost Cycle for Air-to-Water Heat Pump

Autori
Miše, Dino ; Soldo, Vladimir ; Boban, Luka

Vrsta, podvrsta i kategorija rada
Sažeci sa skupova, sažetak, znanstveni

Izvornik
Digital proceedings 17th SDEWES Conference / - , 2022, 27-28

Skup
17th Conference on Sustainable Development of Energy, Water and Environment Systems

Mjesto i datum
Paphos, Cyprus, 06.11.2022. - 10.11.2022

Vrsta sudjelovanja
Predavanje

Vrsta recenzije
Međunarodna recenzija

Ključne riječi
leđenje isparivača ; obnovljivi izvori energije ; dizalice topline ; Zrak kao toplinski izvor
(Evaporator frosting ; renewable energy sources ; heat pumps ; Air source heat pump)

Sažetak
Heat pumps have seen progressive growth in the number of installed units in recent years. The European Heat Pump Association (EHPA) reports a 34% increase in the number of units sold last year compared to 2020. As one of the pillars of the European Strategy 2030 and 2050 in moving away from fossil sources, the research and development of these devices are of great importance. Today, different types of units are used: air, ground, and water source heat pumps. Air source heat pumps dominate the market with both absolute number of sold units and relative change. One of the main drawbacks of the air source heat pumps is reduced capacity in conditions of high relative humidity and low air temperature when the formation of ice on the surface of the heat pump evaporator occurs. Ice accumulated between copper pipes and aluminum fins reduces airflow and acts as additional resistance to heat exchange. With reduced air flow, the ice is unevenly distributed on the evaporator surface and efficiency is significantly reduced. That is why it is essential to control frost formation on the surface of the heat exchanger. Traditional defrosting techniques, which mainly consist of timer-driven defrosting cycles, stop the heating process for long periods or use too much energy, which significantly reduces the system's overall energy efficiency. To overcome the existing problems of an inadequately timed defrosting process and increase the energy efficiency of the system, an improved defrosting system is tested in a psychrometric chamber, a closed room in which it is possible to maintain a consistent temperature and humidity and thereby to simulate the environmental conditions for testing the outdoor unit of the heat pump. The main parameter used for activating digital signals to reverse the process and go into the defrost process is the difference between evaporation and ambient temperature. Temperature difference increases over time due to the weaker heat transfer on the frosted air evaporator and in conducted experiments value is set to 20 K. The end of the defrosting process and the return to the heating mode is determined by the temperature of the external wall of the evaporator which is set to 35 °C. Initial experiments show that parameter driven defrosting reduced the energy for ice melting and evaporating water from the surface of the heat exchanger by up to 40% compared to timer driven system and resulted in up to 8% improvement in overall system efficiency.

Izvorni jezik
Engleski

Znanstvena područja
Strojarstvo

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