Rayin
30-01-2010, 01:04 PM
Dear All
It is indeed a very good site for every one interested in Refrigeration and Air
conditioning. It seems many members out there, are dedicated their whole time for helping
others by providing valuable replies. I am very grateful for the replies/ comments I got for
my previous postings.
Now I am agian seeking another help.
I am in the process of designing a refrigerated cabinet (work top refrigerator) for
vegetable storage, as per the attached Drawing. The overall external area of the cabinet is
5.62 sq. meter. The useful internal space is 0.352 Cubic Meter. The cabinet wall is 50 mm
thick, insulated with PUF (injected in place). The inner most & outer most surface of the wall is of 0.8 mm thick stainless steel sheet. The Cabinet has 2 no. doors of opening size 400x580 mm. This cabinet will be used in a Restaurant kitchen, where the temperature will be +22 to +25 Deg. C. The inside temperature of the cabinet should be +4 Deg. C. Products to be stored are Lettuce, Carrot, Tomato, Spring Onion etc (salad items)
Now my questions are:
1. When calculating wall heat load shall I neglet the 0.8 mm thick stainless steel sheets on
either side of the wall and just consider 50 mm thick PUF only?
2. How to calculate Air Change load?/ Infiltration load ?
3. To calculate product heat load (respiration heat load also), do I need to assume that the
whole cabinet will be filled with products? From where can I get specific volume of
products? As it is for different products, during load calculation, should each product be
taken as equal quantity?
4. The products are brought from super market in refrigerated vehicle, unload in a non-
airconditioned space, then taken to airconditioned (+22 to +25 Deg. C) kitchen, wash and
store in the proposed cabinet. What should be taken as product entering temperature? (I am
in the United Arab Emirates. Here non-refrigerated space temperature can vary 20 to 49 Deg
C, depending on season)
5. Generally what is the pull down time for these type of refrigerated ucabinets?
7. What should be the relative humidity inside the cabinet to keep leaves fresh? How to control RH without using humidity controller?
8. Once the heat load is known shall I use the equation A = Q/(U * Diff. in temperature) to get the evaporator coil length? (Area/ circumfrence)
Anticipating valuable replies, as usual, and thanking all the ladies and gentleman out there
With regards
Rayin
It is indeed a very good site for every one interested in Refrigeration and Air
conditioning. It seems many members out there, are dedicated their whole time for helping
others by providing valuable replies. I am very grateful for the replies/ comments I got for
my previous postings.
Now I am agian seeking another help.
I am in the process of designing a refrigerated cabinet (work top refrigerator) for
vegetable storage, as per the attached Drawing. The overall external area of the cabinet is
5.62 sq. meter. The useful internal space is 0.352 Cubic Meter. The cabinet wall is 50 mm
thick, insulated with PUF (injected in place). The inner most & outer most surface of the wall is of 0.8 mm thick stainless steel sheet. The Cabinet has 2 no. doors of opening size 400x580 mm. This cabinet will be used in a Restaurant kitchen, where the temperature will be +22 to +25 Deg. C. The inside temperature of the cabinet should be +4 Deg. C. Products to be stored are Lettuce, Carrot, Tomato, Spring Onion etc (salad items)
Now my questions are:
1. When calculating wall heat load shall I neglet the 0.8 mm thick stainless steel sheets on
either side of the wall and just consider 50 mm thick PUF only?
2. How to calculate Air Change load?/ Infiltration load ?
3. To calculate product heat load (respiration heat load also), do I need to assume that the
whole cabinet will be filled with products? From where can I get specific volume of
products? As it is for different products, during load calculation, should each product be
taken as equal quantity?
4. The products are brought from super market in refrigerated vehicle, unload in a non-
airconditioned space, then taken to airconditioned (+22 to +25 Deg. C) kitchen, wash and
store in the proposed cabinet. What should be taken as product entering temperature? (I am
in the United Arab Emirates. Here non-refrigerated space temperature can vary 20 to 49 Deg
C, depending on season)
5. Generally what is the pull down time for these type of refrigerated ucabinets?
7. What should be the relative humidity inside the cabinet to keep leaves fresh? How to control RH without using humidity controller?
8. Once the heat load is known shall I use the equation A = Q/(U * Diff. in temperature) to get the evaporator coil length? (Area/ circumfrence)
Anticipating valuable replies, as usual, and thanking all the ladies and gentleman out there
With regards
Rayin