What Are The Optimum Operating Temperatures And Pressures for Ammonia Evaporators?

Temperature and pressure have a significant effect on the performance of an ammonia evaporator:

The effect of temperature:

Refrigeration effect: the lower the evaporation temperature, the stronger the ability of the ammonia evaporator to absorb heat from the surrounding environment, the better the refrigeration effect. However, too low evaporation temperature may lead to increased energy consumption and equipment operating costs.

Heat transfer efficiency: temperature difference is the driving force of heat transfer. If the temperature difference between the evaporation temperature and the medium being cooled is large, the heat transfer efficiency usually increases, but too large a temperature difference may lead to problems such as frosting.

Humidity control: In some applications, such as cold storage, the evaporation temperature affects the relative humidity inside the storage. Excessively low temperatures may lead to excessive dehumidification and affect the quality of stored items.

Effect of pressure:

Refrigerant Flow: Changes in evaporating pressure affect the saturated vapour density of ammonia, which in turn changes the refrigerant flow rate. When the pressure is too low, the flow rate may be insufficient, resulting in a decrease in refrigeration capacity; too high a pressure may increase the load and energy consumption of the system.

Compressor work: evaporating pressure will affect the suction pressure of the compressor. Pressure is too low may make the compressor suction difficulties, or even ‘pumping’ phenomenon, damage to the compressor; pressure is too high may increase the compression ratio of the compressor, reduce its efficiency and service life.

System stability: the appropriate evaporating pressure helps to maintain the stable operation of the refrigeration system. Excessive pressure fluctuations may lead to frequent system starts and stops, affecting the reliability and service life of the equipment.

Generally speaking, in common industrial refrigeration applications, the evaporation temperature of an ammonia evaporator is usually between -30°C and -10°C. In terms of pressure, the corresponding evaporation pressure is between -30°C and -10°C.

In terms of pressure, the corresponding evaporation pressure is usually between 0.1 MPa and 0.3 MPa.

For special refrigeration requirements, such as ultra-low temperature refrigeration or large-scale freezers, the temperature and pressure ranges may vary.

For example, in a large-scale food freezer, the evaporation temperature of an ammonia evaporator may be as low as around -40°C, with a correspondingly lower evaporation pressure.

In some small commercial refrigeration systems, the evaporation temperature may be around -15°C and the pressure adjusted accordingly.

It should be noted that determining the optimum operating temperature and pressure of an ammonia evaporator requires a combination of overall system performance, energy efficiency, safety and refrigeration requirements, and is determined through professional design and commissioning.