Based on the heat transfer equation of the IHX, the optimal
injection pressure for cooling capacity (OIPCC) is:
minjpinj; opt$hh5T1; pinj; opt h1i
¼ meva$hh1 h2Tinjpinj; opt; p1i: (1)
where, pinj,opt is the optimal injection pressure; Tinj is the
saturation temperature at the optimal injection pressure; minj
is the mass flow rate of the injection refrigerant; and meva is
the mass flow rate of the refrigerant passing through evaporator.
Also note that the optimal injection specific enthalpy
can be expressed as following:
hinj; opt ¼ h5T1; pinj; opt: (2)
where, hinj,opt is the optimal injection specific enthalpy.
To sum up, there is an optimal injection condition making
the cooling capacity maximum by subcooling the refrigerant
in main loop to the minimum specific enthalpy.