Description:
A typical freezer application consists of an industrial sized, permanent freezer above a soil or compacted base. One issue resulting from this application involves the ground directly below the freezer heaving due to the moisture in the soil freezing. This heaving can sacrifice the integrity of the structure and should be avoided or mitigated if possible.
Solution:
To remedy the freezing and subsequent heaving of the soil, circulate hot water through piping in the soil to maintain a temperature above freezing. The ideal solution is to heat the soil enough to prevent freezing, while not causing excessive heat to transfer to the freezer itself, reducing efficiency and increasing load on the mechanical systems.
Design:
The design for the necessary supply fluid temperature is extrapolated from ASHRAE heating load calculations. The output of the surface of the soil is dependent on the freezer design. Freezers with internal temperature ranges between 20 °F and 30 °F are designed with loads of 3 BTU/h-ft², the ambient temperature is set at 50 °F directly above the soil, with a maximum ground surface temperature of 55 °F. These assumptions yield a solution that results in the soil staying above freezing (32 °F), while limiting the surface
temperature of the soil as to minimize the negative effects on the freezer mechanical system. As we are not concerned with striping or stratification on the surface, as we would be in a standard heating application, designs are computed around 36” or 48” tube spacing. NOTE: The diameter and length of the tubing are irrelevant when determining a supply fluid temperature and should be selected to optimize cost, availability, and mechanical room and pumping solutions.
Results:
Empirical data shows that the resulting supply fluid temperatures within temperate climates range from 60 °F to 65 °F. With supply fluid temperatures that range close to the ground temperature, the back and edge losses from the soil are negligible. Dozens of these systems have been designed by Watts Radiant and are performing as expected for many years. The best results have been realized when combining intelligent controls that monitor ground temperatures with a heat source that harvests the waste heat produced from the freezer system. By doing this, a hydronic freeze protection system can be an attractive, simple solution that can be run with minimal cost to the owner.
-MDR
A typical freezer application consists of an industrial sized, permanent freezer above a soil or compacted base. One issue resulting from this application involves the ground directly below the freezer heaving due to the moisture in the soil freezing. This heaving can sacrifice the integrity of the structure and should be avoided or mitigated if possible.
Solution:
To remedy the freezing and subsequent heaving of the soil, circulate hot water through piping in the soil to maintain a temperature above freezing. The ideal solution is to heat the soil enough to prevent freezing, while not causing excessive heat to transfer to the freezer itself, reducing efficiency and increasing load on the mechanical systems.
Design:
The design for the necessary supply fluid temperature is extrapolated from ASHRAE heating load calculations. The output of the surface of the soil is dependent on the freezer design. Freezers with internal temperature ranges between 20 °F and 30 °F are designed with loads of 3 BTU/h-ft², the ambient temperature is set at 50 °F directly above the soil, with a maximum ground surface temperature of 55 °F. These assumptions yield a solution that results in the soil staying above freezing (32 °F), while limiting the surface
temperature of the soil as to minimize the negative effects on the freezer mechanical system. As we are not concerned with striping or stratification on the surface, as we would be in a standard heating application, designs are computed around 36” or 48” tube spacing. NOTE: The diameter and length of the tubing are irrelevant when determining a supply fluid temperature and should be selected to optimize cost, availability, and mechanical room and pumping solutions.Results:
Empirical data shows that the resulting supply fluid temperatures within temperate climates range from 60 °F to 65 °F. With supply fluid temperatures that range close to the ground temperature, the back and edge losses from the soil are negligible. Dozens of these systems have been designed by Watts Radiant and are performing as expected for many years. The best results have been realized when combining intelligent controls that monitor ground temperatures with a heat source that harvests the waste heat produced from the freezer system. By doing this, a hydronic freeze protection system can be an attractive, simple solution that can be run with minimal cost to the owner.
-MDR
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