A numerical study on utilizing horizontal flat-panel ground heat exchangers in ground-coupled heat pumps

Techno ‐economic analysis of Al 2 O 3 / CuO nanofluid applied in various horizontal ground heat exchangers

“…To simplify the calculation, the measured NF parameters in Figure 1 were chosen as the boundary conditions for simulation. The underground heat transfer process is controlled by the heat equation, 56 and it can be expressed as: (subscript s represents the soil) In Equation , k s is the thermal conductivity of the soil, c s is the specific heat capacity of the soil, ρ is the density of soil, and T s is the temperature of the soil. In the GHE, the inlet NF temperature needs to be determined based on the outlet NF temperature of the previous iteration and the heat load of the GHE.…”

“…The stationary model is used for the COP analysis in winter, for choosing “days” as a time unit, the transient simulation should be chosen. The data chosen in the simulation can be gotten by the formula 56,57 : where V is the velocity (m/s) of NF, T i is the inlet temperature of NF, m is the mass flow rate, T o is the outlet temperature of NF, ρ is the density of the NF, and A GHE is the cross‐sectional area (m 2 ) of the GHE pipe. Considering that the heat load of the GHE does not only depends on the heat load of the building in research but also the COP of the heat pump.…”

“…In heating mode, the inlet and outlet temperatures of different pipe arrangements and the corresponding COP values are recorded. An independent study of the grid is performed for snake‐type GHE 56 . COP is the dimensionless quantity of the heat‐generating system or refrigeration system that expresses its energy transfer effect.…”

“…The COP of the heat pump is the defining factor that determines the heat load of GHE and the ground is homogeneous in this research. 56 The GSHP system was constructed in COMSOL 5.6 and can be divided into two main parts: the GHE and the heat pump unit. In the GHE, the heat exchange process can be divided into three parts, the convection heat transfer between the NF and the heat exchanger's wall, the heat transfer through the wall of GHE, and the conduction heat transfer between the external surface of the pipes and the soil, so the ground source is modeled as a semi-infinite medium.…”

“…h c can be selected according to different weather conditions and seasons. 56 T amb is the average daily ambient air temperature, the sky temperature T sky , and average daily solar irradiance can be predicted 56 :…”