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From page 21... ... 21 Review of Existing Information on Heat Transfer to Cold Cargo Insulated Cardboard Cartons Containing Dry Ice The manufacturers of insulated packages do not provide any detailed heat transfer performance characteristics of their packages. When this was discussed with the package manufacturers' sales representatives, they said it was the shipper's responsibility to ensure that the proper quantity of dry ice was added to the package. Read the entire page →
From page 22... ... 22 Other Cold Cargo There is a limited amount of technical literature on heat transfer modeling of cold packages in transit.37 For example, Kumar and Panigrahi modeled frozen fish placed in polyforminsulated cardboard cartons.38 Heat Transfer Calculations Heat Transfer to Packages As long as the thickness of the insulating material is much less than the dimensions of the sides of the package, the steady-state heat transfer rate can be modeled using the following equation: Q UA T= ∆ where Q = rate of heat transfer, W, U = overall heat transfer coefficient, W/m2 K, A = package area, m2, and DT = temperature difference between dry ice sublimation temperature and cargo bay temperature, K The overall heat transfer coefficient U can be broken into components by considering the reciprocal of the coefficient to be a resistance that is made up of several resistances to heat transfer: one at the outside wall, another through the insulation, a third at the inside wall, and if necessary, the resistance at the surface of the dry ice. Read the entire page →
From page 24... ... 24 two-dimensional model had been used, the temperature drop between the surface of the package and the ambient air would have been lower on the corners, lowering the rate of heat gain and therefore the calculated rate of sublimation. Another uncertainty is in the thermal conductivity of the EPS. Read the entire page →
From page 25... ... 25 Many details of heat transfer can be included in a model: heat transfer to the inside wall of the box, the thermal conductivity of the EPS foam insulation, the thermal conductivity of the cardboard, free or forced convection on the outside of the box, contact resistances, radiation losses, and so forth. But looking at the heat transfer model carefully, nearly all of the resistance to heat transfer is determined by the thickness of the EPS foam; everything else is either negligible or small. Read the entire page →

From page 21...

... 21 Review of Existing Information on Heat Transfer to Cold Cargo Insulated Cardboard Cartons Containing Dry Ice The manufacturers of insulated packages do not provide any detailed heat transfer performance characteristics of their packages. When this was discussed with the package manufacturers' sales representatives, they said it was the shipper's responsibility to ensure that the proper quantity of dry ice was added to the package.

Read the entire page →

From page 22...

... 22 Other Cold Cargo There is a limited amount of technical literature on heat transfer modeling of cold packages in transit.37 For example, Kumar and Panigrahi modeled frozen fish placed in polyforminsulated cardboard cartons.38 Heat Transfer Calculations Heat Transfer to Packages As long as the thickness of the insulating material is much less than the dimensions of the sides of the package, the steady-state heat transfer rate can be modeled using the following equation: Q UA T= ∆ where Q = rate of heat transfer, W, U = overall heat transfer coefficient, W/m2 K, A = package area, m2, and DT = temperature difference between dry ice sublimation temperature and cargo bay temperature, K The overall heat transfer coefficient U can be broken into components by considering the reciprocal of the coefficient to be a resistance that is made up of several resistances to heat transfer: one at the outside wall, another through the insulation, a third at the inside wall, and if necessary, the resistance at the surface of the dry ice.

Read the entire page →

From page 24...

... 24 two-dimensional model had been used, the temperature drop between the surface of the package and the ambient air would have been lower on the corners, lowering the rate of heat gain and therefore the calculated rate of sublimation. Another uncertainty is in the thermal conductivity of the EPS.

Read the entire page →

From page 25...

... 25 Many details of heat transfer can be included in a model: heat transfer to the inside wall of the box, the thermal conductivity of the EPS foam insulation, the thermal conductivity of the cardboard, free or forced convection on the outside of the box, contact resistances, radiation losses, and so forth. But looking at the heat transfer model carefully, nearly all of the resistance to heat transfer is determined by the thickness of the EPS foam; everything else is either negligible or small.

Read the entire page →

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