Data for refrigeration system design

Design tasks and known conditions

    According to the requirements, in Wuhan, to fan coil terminal device, chilled water temperature of 7 deg.C, air-conditioning return temperature is 11 deg.C, total amount of refrigeration of 400KW, cooling water system using cooling tower circulating water.

Determine the number and type of refrigeration compressor

1.Determine the total cooling capacity of the refrigeration system

   The total cooling capacity of the refrigeration system should include the amount of refrigeration required by the user, and the cooling system itself and the cooling loss of the cooling system, and can be calculated by pressing:

In pressing:

   ---the total cooling capacity of the refrigeration system(KW)

   --- the amount of refrigeration required by the user(KW)

A---Cold loss coefficient

1.General for indirect cooling system, when the air conditioning cooling capacity is less than 174KW, A=0.15~0.20; when the refrigeration capacity of air conditioner is 174~1744KW, A=0.10~0.15; when the air conditioning refrigerating capacity greater than 1744KW, A=0.05~0.07; for direct cooling system, A=0.05~0.07.

2. Determine the type and system of refrigerants

   According to the design requirement, ammonia is used as refrigerant and indirect cooling mode is used.

3.determine the working condition of refrigeration system design

   Determine the working condition of refrigeration system design mainly refers to determine the evaporation temperature, condensation temperature, the compressor suction temperature and cold temperature and other parameters. The determination of the main work parameters reference "refrigeration engineering design manual" to calculate.

   When condensation temperature is determined, the condenser cooling water inlet and outlet water temperature should be determined according to the use of cooling water.

A.Determination of condensation temperature

From the "refrigeration engineering design manual" in the summer of the Wuhan area is not guaranteed outdoor average annual 50h wet bulb temperature(℃) .

For the use of the circulating water system of cooling tower, cooling water inlet temperature is calculated according to the following formula:

In formula: ---Cooling water inlet condenser temperature(℃)

--- the wet bulb temperature of the 50h is not guaranteed at the average annual outdoor summer(℃).
--- safety values for mechanical ventilation cooling tower, =2~4℃.
The temperature of the cooling water condenser is related to the temperature of the condenser and the form of the condenser.

According to the below formula:

Selection of vertical shell tube condenser:= +(2~4)=31.2+3=34.2℃

Attention:Usually no more than 35℃

System with water as cooling medium, the heat transfer temperature difference from 4 ~ 6 ℃, the condensing temperature    ℃
In formula, ---the condensing temperature(℃)

Selection of condenser is calculated

1.The principle of choosing condenser
Condenser choice depends on the local water temperature, water quality, water, climate conditions, and factors such as compressor plant layout requirements. Generally higher in poor water quality of cooling water, water temperature, water is adequate, appropriate USES vertical condenser. Wuhan district cooling water temperature is higher, so choose vertical shell and tube condenser.
2.Condenser heat load calculation
Condenser heat load can be pressed type calculation:
The heat load of the condenser (KW)
--- the actual exhaust enthalpy of the compressor (KJ/Kg) 
--- Indication efficiency of compressor

3.Condenser heat transfer area computation
- heat transfer area of the condenser ().
- the heat transfer coefficient of condenser [].
- the logarithmic mean temperature between refrigerant and cooling medium
Vertical shell and tube type ammonia refrigerant condenser K = 700 ~ 800 w /.
- allowance for 10% ~ 15%.
The compressor matching condenser LN - 120 shows that the heat transfer area of 120 ㎡﹥109.648 ㎡ meet the requirements.

4.The calculation of condenser cooling water:
5.Cooling tower cooling water volume calculation:
Calculation of evaporator selection
1.The principle of selecting the evaporator
Evaporator in the form of choice, should according to the types of refrigerant and cooling, and determine the structure of air conditioning system treatment chamber. If the treatment room to use water cooled surface air coolers, with ammonia as refrigerant, appropriate USES horizontal shell and tube evaporator. So, this design adopts horizontal shell and tube evaporator in the refrigeration system.
2. The evaporator heat transfer area computation
a.heat transfer temperature difference:
b.heat transfer coefficient K to check the cooling technology P156 table 8 ~ 2: K is 500 ~ 500 here take K = 550
c,.heat transfer area:
Given the 10% ~ 15% of the amount of rich Ac (s) = 119.65 x (1 + 0.15) = 137.5975 ㎡
The compressor matching condenser DWZ - 150 shows that the heat transfer area of 150 ㎡ > 137.5975 ㎡ meet the requirements.
3.Cooling water circulation quantity calculation:

Selection and calculation of other auxiliary equipment

1.The choice of the receiver is calculated
Receiver is calculated according to the volume of refrigerant circulation, but the largest storage capacity shall be no more than an hour of 1/3 ~ 1/2 refrigerant total circulation. At the same time, should be considered when the environmental temperature change, receiver inside the liquid refrigerant risk caused by thermal expansion, drum its storage capacity is generally not more than the whole volume of 70% ~ 80%.

The volume of the reservoir is calculated by the following formula:
From the supporting 1.5B - ZA, it can be known as: 1.5 > 1.279 meet the requirements.
2.Selection and calculation of oil ammonia separator 
Oil separator cylinder diameter:
Compressor matching YF - 40 of 273 mm diameter > 215 mm meet the requirements.
3.The choice of the gas-liquid separator is calculated
Barrel diameter of vapor liquid separator according to the following formula:
Form a complete set of AF - 80 barrel diameter: 400 mm > 392.33 mm to meet the requirements.
4.The selection of oil trap is calculated
Oil trap selection is based on experience, when the refrigerating capacity of the refrigeration station for 300 ~ 600 KW, with 219 mm oil trap. Models for: JY - 200.
5.Selection and calculation of the non-condensable gas separator
In general, a system is equipped with an air separator, only when the refrigerating capacity of the refrigeration station standard working conditions is less than 1163 kw, appropriate USES a small (108 mm) barrel diameter of air separator. According to the above conditions: KF - 32 b to meet the requirements.

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