The influence of the evaporating temperature change in the cooling circulating water machine
For the temperature change of the chiller, different temperatures have different effects.
After the size of the cooling load and operating temperature conditions are confirmed, the required cooling capacity and shaft power can be calculated. However, during the operation of the cooling cycle water machine Chiller refrigeration system, the temperature conditions used are often changed, which affects the refrigeration capacity and shaft power.
When the condensing temperature is unchanged and the evaporating temperature is 0°C, -15°C, -30°C, the changes in cooling capacity and shaft power are as follows:
After the evaporating temperature is changed, the cooling capacity per unit weight q=i1-i6 is also changed. When the evaporating temperature is 0℃, -15℃, -30℃, the q value changes.
The evaporating temperature changes by 15°C, and the q value changes by 5kcal/kg, which accounts for about 1.85% of the entire refrigeration capacity. After the evaporating temperature changes, the specific volume of the suction gas is also significantly changed, which greatly changes the weight and fluid quality of the refrigerant. It can be seen from the formula Q=Vh/υ1ηv(i1--i6) that when the volumetric efficiency ηv is unchanged and the theoretical displacement of the refrigerator is the same, the lower the evaporation temperature and the larger the υ1, the smaller the weight flow of the refrigerant. The cooling capacity will then be greatly reduced.
When the evaporation temperature rises from -15°C to 0°C, the suction pressure nearly doubles, while the refrigerant weight flow rate increases by 76%, that is, the cooling capacity increases by 76%; and when the evaporation temperature drops from -15°C to -30°C When the weight flow is reduced by 53%, the cooling capacity is reduced by 53%. It can be seen that when the evaporation temperature rises by 15°C and when it drops by 15°C, the rate of change of the refrigeration quality is different.