Heat load for cold store

[Sandro Baptista]

Hi Guys,

When I do calculation of the heat loads on a refrigerated space I always count with a % for the ice formation on the coil, unless the temperature of the coil is high enough to ice formation.

During ice formation the latent heat needed for the solidification of the water steal refrigeration capacity and so the air can't down so much is air temperature.

Never had see this kind of heat load written on the engineering books but the true is that kind of heat load exist. Also never had see any one have this effect on account.

Any comments?

[Tesla]

You need to research your subject further. You are incorrect - there is favorable ice formation to a certain extent, check massey university. It increases heat transfer. Then check coil bypass factor.

[Sandro Baptista]

You need to research your subject further. You are incorrect - there is favorable ice formation to a certain extent, check massey university. It increases heat transfer. Then check coil bypass factor.

Sorry Tesla, BUT you are confusing/mixing the facts. I didn't mentioned about heat transfer efficiency, this is another subject. I'm talking about heat loads on a system/"box" where you must remove extra heat to frozen water.

[mad fridgie]

You are talking about "air infiltration" and is a standard part of design in your heat load calculations.
You need to know both wet and dry bulb conditions and how many air changes you expect

[RANGER1]

Sandro,
All I know is most clients want cheapest job so air coolers are supplied for heat load etc etc .

All looks good on paper but usually rooms don't perform or struggle due ,

1/ Not allowing for a lot of defrosts if necassary so unit is not cooling in this period/s

2/Not allowing for enough surface area on unit that has a % of ice on it in normal operation.

Usually this means air coolers are 50% bigger than "normal".
As you say for freezer or below 0 deg applications .
Most don't perform when you want them to in summer etc.

[Sandro Baptista]

You are talking about "air infiltration" and is a standard part of design in your heat load calculations.
You need to know both wet and dry bulb conditions and how many air changes you expect

Air infiltrations don't account the solidification of the water but only cooling and condensate. Besides that part of this water come from the product, then after it condensate it will be transform on ice (latent heat) so part of the cooling capacity will be used to the ice formation.

[Lodiev]

Yes Sandro you are correct. When designing a cold/freezer room u have to know the entering temp of the product, the dew points of the product when placed in a freezer. The big thing is that u do not want to dry out the product and thus we normally bring down the superheat on the evaporators and up the surface area to get the same heat transfer(Kw r). Defrosting to many times also dry out the product especially if the product are not in plastic bag but open to the room atmosphere. Have u ever seen the moist that forms on the surface of any product after a long defrost period and the cooling cycle went back on? This moist forms because the skin of the product are giving of water as it is going through a dew point.
Hope i explained it so that u understand that design differs from room to room depending on the product that are going to be stored.

[Lodiev]

Yes Sandro you are correct. When designing a cold/freezer room u have to know the entering temp of the product, the dew points of the product when placed in a freezer. The big thing is that u do not want to dry out the product and thus we normally bring down the superheat on the evaporators and up the surface area to get the same heat transfer(Kw r). Defrosting to many times also dry out the product especially if the product are not in plastic bag but open to the room atmosphere. Have u ever seen the moist that forms on the surface of any product after a long defrost period and the cooling cycle went back on? This moist forms because the skin of the product are giving of water as it is going through a dew point.
Hope i explained it so that u understand that design differs from room to room depending on the product that are going to be stored.