Page 356 - Defrosting for Air Source Heat Pump

352 Appendices

Appendix F: Program listing of Model 1 in Section 4.2

The following program written in Matlab R2012a was used for a modeling study of the
negative effects of the downward flowing of melted frost on defrosting performance
for an ASHP unit having a vertically installed three-circuit outdoor coil during reverse
cycle defrosting without using any water-collecting trays between circuits; this is
named Model 1 in Chapter 6 in this thesis.
clear all;
clc;
hri=zeros(45,3); % the enthalpy value of input refrigerant, kJ/kg
Mr=zeros(45,3); % the mass flow rate of refrigerant, kg/s
Tri=zeros(45,3); % the temperature of input refrigerant, °C
Rr=zeros(45,3); % thermal resistance of refrigerant during
2
defrosting, (K˙m )/W
% input all the known parameters
hri=xlsread(’song20130828’,’hri’);
Mr=xlsread(’song20130828’,’Mr’);
Tri=xlsread(’song20130828’,’Tri’);
Rr=xlsread(’song20130828’,’Rr’);
% input all the known parameters from the excel with the experimen-
tal results
mf=zeros(45,3); % the mass of melted frost, when it comes to 4th
stage, it is 0 kg/5s
Tw=zeros(45,3); % the temperature of retained water on the coil, °C
qr=zeros(45,3); % the energy used from the refrigerant during the
5 seconds, J
qr2=zeros(46,3); % use refrigerant (R22) to calculate the energy
used in defrosting; and another way is to measure and calculated
the energy used with Power system, J
Tro=zeros(45,3); % the temperature of exit refrigerant, °C
qm=zeros(45,3); % the energy used in frost melting during the
5 seconds, J; melting and energy comes from the refrigerant, J
sfrost=zeros(45,3); % the total mass of frost melted before the
moment, kg
qair=zeros(45,3); % the energy used in the ambient air, J
hair=zeros(45,3); % the coefficient of natural convective heat trans-
2
fer, W/(m °C)
mvaw=zeros(45,3); % the mass of vaporized water into the ambient
air, kg/5s
smvaw=zeros(45,3); % the sum of vaporized water before this moment, kg
mrw=zeros(45,3); % the mass of retained water on this coil, kg/5s
2
hd=zeros(45,3); % the coefficient of convective mass transfer, W/(m °C)
qvap=zeros(45,3); % the energy used in the water vaporized, J
s_qvap=zeros(45,3); % total energy used in the water vaporized, J
watertray=zeros(45,3); % the mass of water flowing away from the
water collecting tray, kg/5s