Page 81 - Defrosting for Air Source Heat Pump

Modeling study on uneven defrosting 73

4.2 Semiempirical modeling study

4.2.1 Development of two semiempirical mathematical models
As shown in Fig. 4.1 and Table 4.1, two semiempirical models were developed based
on whether water-collecting trays were installed between circuits. Model 1 was devel-
oped for the condition when only one water-collecting tray (Tray C) was installed
under the lowest circuit, Circuit 3, and connected to a water-collecting cylinder
(Cylinder C), that is, no water trays were installed between circuits. However, Model
2 was for the condition when three water-collecting trays (A, B, and C) were each
placed under Circuits 1–3, and connected to three cylinders (A, B, and C), respec-
tively. When developing the two mathematical models, the entire airside of the

Outdoor coil (air side)
Refrigerant in

m w,j –1T w,j –1 Circuit 1

m w,jT w,j m f,j Circuit 2

Circuit 3 Water collecting tray C
m w, j+1T w,j+1
Refrigerant out
C Water collecting cylinder C

Model 1

Refrigerant in

m w,j –1T w,j –1 Circuit 1 Water collecting tray A

A m f,j
m w,jT w,j
Circuit 2 Water collecting tray B
B
m w, j+1T w,j+1 Circuit 3 Water collecting tray C
Refrigerant out
C Water collecting cylinder A, B, C

Model 2
Thermal-couple
Fig. 4.1 Conceptual models for the airside of a three-circuit outdoor coil.