How is the Cooling Load Calculated?
What is a cold room?
It is used to slow down degradation and keep fresh as long as possible in cold room, fruit vegetables and meat products. Heat is a factor that accelerates the deterioration of products. For this reason, the heat in the cold rooms is removed and the products are cooled.
In order to remove heat from the environment and ensure that the stored products are stored as long as possible, cooling systems are required to ensure correct and automatic control of the temperature.
In order to remove heat from the environment and perform a proper cooling process, it is necessary to calculate the cooling load. Cooling load; the product stored in the warehouse, the area to be installed in the warehouse varies according to the way the warehouse is used, so in most cases the average cooling load is calculated and the cooling capacity of the system to be installed is calculated accordingly.
Cold Room Heat Sources
Heat recovery in cold rooms usually passes through transmission loads of 5-15%. In other words, there is a thermal energy flowing from the roof, walls and floor of the tank into the cold room.
The heat always flows from the heat to the cold and the interior of the cold room is much colder than the surrounding environment, so the heat always tries to enter the area due to this temperature difference. If the cold store is exposed to direct sunlight, the heat transfer will be higher.
Another factor affecting the cooling load is the loads from the products placed in the tank. Cooling loads from products constitute 55-75% of the total heat gain. In addition, if the product has cooled down after a second freezing, freezing or advanced cooling, it will generate additional cooling load.
When calculating the heat gain, it is necessary to take into account the packaging, because the package of the product will be subjected to cooling in the tank.
In addition, if the fruits and vegetables are to be cooled, these products must be taken into account and the heat gain from this area should be taken into account because they produce some heat in the environment by breathing.
The next thing to consider is the internal loads of about 10-20%. This is the heat gain from equipment such as temperatures, forklifts, lighting, etc. given by people working in a cold room. For this reason, factors such as the equipment to be used for loading and unloading the products from the warehouse, the number of personnel to work in the warehouse, the time spent for loading / unloading should be included in the heat gain account.
In addition, we need to consider the cooling equipment in the room, which will account for approximately 1-10% of the total cooling load. For this, it is necessary to know the degree of the fan motors and how long they will operate every day and the heat that the evaporator will give to the environment when defrosting.
The last thing to consider is air leaking into the room, which affects 1-10% of the cooling load again. This occurs when the cold room door is opened. The other is ventilation. Because fruits and vegetables emit carbon dioxide, they require a ventilation fan in some warehouses. This air must be included in the heat gain account as it must be cooled.
Example of cooling load calculation
An example of a simplified cooling load calculation for a cold room can be found in the attached pdf file.