Nominal cooling capacity of the expansion valve in the refrigeration unit
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Among the parameters of the expansion valve used in a refrigeration unit, there is a value known as the nominal cooling capacity. This value represents the product of the weight of the refrigerant passing through the expansion valve under certain nominal operating conditions and the difference between the enthalpy values of the refrigerant at the inlet and outlet of the expansion valve; in other words, it represents the cooling capacity of the expansion valve under those operating conditions. We currently have a 9P refrigeration unit. The 9P figure refers to the input power, which is approximately 6.6 kW. It uses a semi-hermetical piston compressor from Bitzer, with R404a as the refrigerant. The expansion valve is a Danfoss TES2 068Z3403 model with valve element number 5. The nominal cooling capacity of this unit is 7.7 kW. Based on these figures, when the unit operates under its nominal conditions, its energy efficiency ratio is only around 7.7/6.6 = 1.17, which is far below the 3 or 4 levels expected. Could it be that the expansion valve used is not suitable? Or is there a significant difference between the actual cooling capacity and the nominal cooling capacity of the expansion valve during operation?
Chilling units are usually purchased as complete systems as needed. If the design requirements are not met during use, it is best to consult a design institute or designer to find a solution. There are many factors that prevent it from meeting the usage requirements.
When making the purchase back then, we turned to a company that specializes in refrigeration unit modifications; now we want to switch to continuous cooling equipment, but the original supplier can no longer provide technical support
An expansion valve is essentially something like a throttle valve or a stop valve. Its function is merely that of a valve to control flow. Most of the valves installed on refrigeration units are temperature-controlled valves, and they are set according to the overall cooling capacity of the unit. If continuous cooling is used, an increase in energy consumption is required to enable continuous operation. It is recommended not to change the engine set.
The full-load input is 9P, but that doesn’t mean the half-load input is also 9P. When the operating conditions are adjusted, the input current will also change, right?
Modification of the expansion valve in refrigerators – this has been done in large-scale units; the principle is similar to that used on the 4th floor, where the liquid refrigerant is converted into a gas-liquid mixture to facilitate evaporation. The latest approach seems to involve electronic expansion valves. The valve opening is controlled by the intake temperature. Or superheat control.