![]() These will generate heat as they are still alive, that’s why we’re cooling them to slow them down their deterioration and preserve them for longer.įor this example I’ve used 1.9kJ/kg per day as an average but this rate changes over time and with temperature. Next we calculate the product respiration, this is the heat generated by living products such as fruit and vegetables. Q = m x Cp x (Temp enter – Temp store) / 3600 Temp store = the temperature within the store (☌).Temp enter = the entering temperature of the products (☌).m = the mass of new products each day (kg).CP = Specific Heat Capacity of product (kJ/kg.☌).Q = m x Cp x (Temp enter – Temp store) / 3600. There are 4,000kg of new apples arriving each day at a temperature of 5☌ and a specific heat capacity of 3.65kJ/kg.☌. Next we will calculate the cooling load from the product exchange, that being the heat brought into the cold room from new products which are at a higher temperature.įor this example we’ll be storing apples, we can look up the specific heat capacity of the apples but do remember if you’re freezing products then the products will have a different specific heat when cooling, freezing and sub cooling so you’ll need to account for this and calculate this separately, but in this example we’re just cooling. Remember if your cold room is in direct sunlight you’ll need to account for the suns energy also. ![]() Total daily transmission heat gain = 22kWh/day + 1.8kWh/day = 23.8kWh/day If the floor isn’t insulated then you will need to use a different formula based on empirical data. Q = U x A x (Temp out – Temp in) x 24 ÷ 1000 Then we can run these numbers in the formula we saw earlier, you’ll need to calculate the floor separately to the walls and roof as the temperature difference is different under the floor so the heat transfer will therefore be different. To calculate “A” is fairly easy, its just the size of each internal walls, so drop the numbers in to find the area of each wall, roof and floor. Temp out = The ambient external air temperature ( ☌).Temp in = The air temperature inside the room ( ☌).A = surface area of walls roof and floor (we will calculate this) (m 2).U = U value of insulation (we already know this value) (W/m 2.K).Q = U x A x (Temp out – Temp in) x 24 ÷ 1000. To calculate the transmission load we will be using the formula Just to note the manufacturer should tell you what the u value is for the insulation panels, if not, then you will need to calculate this. The walls, roof and floor are all insulated with 80mm polyurethane with a U value of 0.28W/m 2.K.The ambient air is 30 °c at 50% RH, The internal air is 1 ☌ at 95% RH.The dimensions of our cold store are 6m long, 5m wide and 4m high.Now If you’re doing this for a real world example then I recommend you use a design software such as the Danfoss coolselector app for speed and accuracy. Lets consider a simplified example of a cooling load calculation for a cold room. Cooling load calculation – Cold room worked example Fruit and vegetables give off carbon dioxide so some stores will require a ventilation fan, this air needs to be cooled down so you must account for this if it’s used. ![]() This occurs when the door opens so there is a transfer of heat into the space through the air. The last thing we need to consider is infiltration which again adds 1-10% to the cooling load. To remove the heat we use a refrigeration system as this allows accurate and automatic control of the temperature to preserve the goods for as long as possible. Heat accelerates their deterioration so the products are cooled down by removing the heat. Learn more about Cold Room solutions here What is a cold room?Ī cold room is used to store perishable goods such as meat and vegetables to slow down their deterioration and preserve them as fresh as possible for as long as possible. ![]() Go green and get ahead of competition without Their wide range of products and market-leading application expertise enable you to think ahead and meet future refrigerant and energy regulations. With Danfoss, you can build sustainable and efficient cold rooms. Want free cold room calculation design software?ĭownload Coolselector®2 for free -> Click here Scroll to the bottom to watch the video tutorial. We’ll first look at the heat sources and then we’ll look at a worked example of how to perform a cold room cooling load calculation in a simplified example. In this article we’ll be looking at how to calculate the cooling load for a cold room.
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