Abstract
The efficiency of a heat pump energy system is significantly influenced by its low-temperature heat source. This paper presents the results of operational monitoring, analysis and comparison of heat transfer fluid temperatures, outputs and extracted energies at the most widely used low temperature heat sources within 218 days of a heating period. The monitoring involved horizontal ground heat exchangers (HGHEs) of linear and Slinky type, vertical ground heat exchangers (VGHEs) with single and double U-tube exchanger as well as the ambient air. The results of the verification indicated that it was not possible to specify clearly the most advantageous low-temperature heat source that meets the requirements of the efficiency of the heat pump operation. The highest average heat transfer fluid temperatures were achieved at linear HGHE (8.13 ± 4.50 °C) and double U-tube VGHE (8.13 ± 3.12 °C). The highest average specific heat output 59.97 ± 41.80 W/m2 and specific energy extracted from the ground mass 2723.40 ± 1785.58 kJ/m2·day were recorded at single U-tube VGHE. The lowest thermal resistance value of 0.07 K·m2/W, specifying the efficiency of the heat transfer process between the ground mass and the heat transfer fluid, was monitored at linear HGHE. The use of ambient air as a low-temperature heat pump source was considered to be the least advantageous in terms of its temperature parameters.
Highlights
Conventional heating, ventilation and air conditioning (HVAC) systems use fossil fuels and contribute significantly to deterioration of environmental quality [1]
Temperatures of the Heat Transfer Fluids Supplied to the Heat Pump Evaporators
The verification results showed that it was very difficult to specify the most advantageous low-temperature heat source fulfilling the requirements of the efficiency of heat pump operation
Summary
Conventional heating, ventilation and air conditioning (HVAC) systems use fossil fuels and contribute significantly to deterioration of environmental quality [1]. Energy systems using renewable and sustainable sources of energy, and allowing the use of the part of energy called anergy (unusable in the sense of the 2nd Law of Thermodynamics), can be considered in the above sense as efficient systems with a high potential to meet the requirements of reducing fossil fuel consumption and environmental protection. These requirements are very well fulfilled by energy systems with heat pumps. Water, rock and ground masses are the most widely used low-temperature energy sources for heat pumps
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