PROBLEM IN DIRECTLY APPLYING THE GSSM TO MPHX USING CAPILLARY TUBES FOR FLOW CONTROL
In GSSM, the mass flow rates of refrigerant in paths are iteratively adjusted until the pressure drops of refrigerant in all paths from inlet to outlet are equal.
Incorrect results may occur if we directly apply the above GSSM to the MPHX using capillary tubes for flow control, especially for the cases that the mass flow rate of refrigerant calculated from Equation 4 for one capillary tube is larger than the choked value.
The simulation result with the GSSM is incorrect due to the unavoidable refrigerant-lost problem in the algorithm.
BASIC IDEA IN EXTENDING THE GSSM TO MPHX USING CAPILLARY TUBES FOR FLOW CONTROL
The refrigerant-lost problem that occurred in GSSM is mainly caused by the extra constraint on the maximum mass flow rate of refrigerant for MPHX using capillary tubes for flow control, and the cause of the refrigerant-lost problem is different for different cases of the choked refrigerant flows.
The reason for the occurring refrigerant-lost problem in GSSM for this case is that the assumed value is larger than the choked value for [m.sub.c] number of refrigerant flows, as shown in Equation 5b.
The reason for producing discrepant mass flow rate of refrigerant in GSSM for this case is that the given total mass flow rate of refrigerant in the heat exchanger conflicts with the inlet state of refrigerant and the geometry parameters of the capillary tubes.
Finally, a very small value of the total mass flow rate of refrigerant may be obtained after the simulation with the GSSM. Therefore, auxiliary equations should be introduced to determine the right value of the mass flow rate of refrigerant in each path to avoid such repeat of the refrigerant-lost problem occurring in GSSM.
If capillary tube is not used, [DELTA][p.sub.r, 1j, cap] and [DELTA][p.sub.r, 1j, dc] in Equation 14 are equal to 0, Equation 14 becomes the same as that in the previously developed GSSM (Liu et al.
If all refrigerant in capillary tubes on all paths are choked during the iteration process of solving the refrigerant distribution among the paths, an incorrect and much smaller value of the mass flow rate of refrigerant may be obtained after simulation with the GSSM because the [M.sub.r,1] refrigerant is always lost during the iteration process for determining the refrigerant distribution among the subpaths.
So the heat-transfer calculation algorithm in the previously developed GSSM (Liu et al.