The thermal expansion valve is an important regulating component in the refrigeration system. Its main function is to adjust the refrigerant flow entering the evaporator to adapt to changes in the evaporator load, thereby maintaining efficient operation of the system. According to the structure and pressure sensing position, thermal expansion valves can be divided into two types: internally balanced type and externally balanced type.
The internally balanced expansion valve is suitable for systems with small resistance loss in the evaporator pipeline. In this type of expansion valve, the pressure at the evaporator inlet is felt below the diaphragm. Since the resistance loss of the evaporator pipe is small, the pressure difference between the evaporator inlet and outlet is not large. The internally balanced expansion valve can accurately adjust the refrigerant flow to ensure stable operation of the system.
On the other hand, externally balanced expansion valves are suitable for refrigeration systems with large resistance losses in the evaporator pipe. In this type of expansion valve, the pressure at the evaporator outlet is felt below the diaphragm. Due to the large resistance loss in the evaporator pipe, if an internally balanced expansion valve is used, the actual pressure at the evaporator outlet will be significantly lower than the pressure at the inlet, which may lead to inaccurate adjustment and thus affect system performance. By sensing the pressure at the evaporator outlet, the externally balanced expansion valve can more accurately reflect the actual working conditions in the evaporator, thereby more effectively controlling the refrigerant flow and adapting to larger pressure losses.
This difference in design determines the applicability of internally balanced and externally balanced expansion valves under different working conditions. The internally balanced expansion valve has a simple structure and is suitable for small and low-pressure loss refrigeration systems, while the externally balanced expansion valve is suitable for large-scale and high-pressure loss systems and can provide higher control accuracy and stability.
To sum up, choosing the right type of thermal expansion valve is crucial to the efficiency and stability of the refrigeration system. During the design and selection process, the resistance loss of the evaporator pipe must be fully considered to ensure that the system can operate at its best.
