What Does Defrosting And Defrost Cycle Mean In Construction?
What Does Defrosting And Defrost Cycle Mean In Construction?
The term “defrosting” in construction refers to the process of melting any ice that has accumulated on the cooling coils of refrigerant equipment.
This is usually done through a defrost cycle, which is an automated process that turns off the refrigeration cycle and allows any ice build up to melt off the coils.
In some specialty coolers, there is an actual heating cycle that heats the coils to facilitate defrosting.
The defrost cycle can be electric or off-cycle, with electric providing a more positive defrost with shorter durations.
Upon termination of the defrost cycle, there may be a pumpdown period where the system will run for a few minutes to ensure all liquid refrigerant has been removed from the evaporator before restarting.
A freeze-thaw cycle is different from a defrost cycle in that it refers to the freezing and thawing of water inside pipes associated with winter months.
This can cause concrete components such as foundations, driveways and sidewalks to become prone to cracking, crumbling or rupture due to water absorption during warm days and freezing on cold days.
How Does A Defrost Cycle Work?
A defrost cycle in refrigerant equipment is a self-maintenance mechanism that runs when the heating component attached to the evaporator coil is activated.
During the defrost, the coil runs hot to melt accumulated frost and ice, allowing the evaporator to resume its optimal heat absorption and freezer cabinet cooling functions.
The defrost cycle is normally time-initiated and temperature-terminated, with a fail-safe time backup.
The heat produced is just enough to melt the ice accumulated on the evaporator without causing frozen foods to become rancid and spoil.
Refrigerators/freezers with automatic defrost system prevent ice build-up in the unit by automatically defrosting the evaporator regularly.
This involves running a fan on the compressor and an electric timer for an efficient operation.
The primary advantage of automatic defrost units is easy maintenance as it eliminates the need for manually defrosting and cleaning the unit.
Refrigeration units without auto-defrost system require manual defrosting, which involves removing all food from the unit and turning it off to melt built-up ice.
What Are The Types Of Defrost Cycles?
There are several types of defrost cycles used in refrigerant equipment. Manual defrost is the oldest method and involves removing all food from the refrigerator and allowing it to defrost naturally.
Off cycle defrost involves temporarily pausing or ceasing the refrigeration cycle, causing the evaporator temperature to increase.
Cycle defrost occurs during the regular on/off cycle of the compressor, where the evaporator is in fact defrosted.
Adaptive defrost uses electronic controls to determine when too much frost has built up and will only occur when necessary.
Supplementary heat defrost uses a heating element to melt any ice that has built up on the evaporator coils.
What Are The Benefits Of Defrosting In Construction?
The main benefit of the defrost cycle in construction is that it helps to prevent frost from building up on the outdoor coil of a heat pump.
This is important as frost buildup can reduce airflow and impede the efficiency of the system. The defrost cycle works by reversing the flow of refrigerant and activating a heating element to warm up the outdoor coil, melting any frost that has accumulated.
The two main types of defrost cycles are electric defrost and hot gas defrost. Electric defrost uses electric heaters to warm up the outdoor coil, while hot gas defrost uses hot gas to do so.
Hot gas defrost is more energy efficient than electric defrost as it directs 70% of its heat energy towards melting the frost, while electric defrost requires more power input from its heaters.
Additionally, hot gas defrost has shorter durations than electric defrost, allowing for extended operation time during the day.
What Are The Disadvantages Of Defrosting In Construction?
The main disadvantage of manual defrosting in construction is that it takes too much time.
This can be especially problematic in cold climates where freeze-thaw cycles occur frequently, as the process of manually defrosting concrete or other hardscaping elements can be labor-intensive and time-consuming.
In addition, manual defrosting can lead to increased current consumption, which can add to the cost of construction.
Furthermore, manual defrosting may not be effective in preventing freeze-thaw damage if the concrete or hardscaping elements are not mixed, air-entrained, or cured adequately.
Finally, manual defrosting may not be able to prevent frost heaving and subsidence caused by thawing permafrost, which can lead to structural damage and costly repairs.
Therefore, it is important for builders to take precautions such as using deicing chemicals and optimizing the use of fly ash in concrete to prevent freeze-thaw damage.
How To Prevent Defrosting In Construction?
To prevent defrosting in construction, contractors can use insulation such as blankets and straw to cover the ground and prevent it from freezing.
Additionally, ground thaw products such as construction heater blankets and hydronic surface heaters can be used to thaw frozen ground before a concrete pour.
Deicing chemicals such as sodium chloride, calcium chloride, magnesium chloride, and potassium chloride can also be used to reduce the freezing point of precipitation.
Finally, air entrainment admixtures such as Air Plus or Super Air Plus can be added to concrete to create microscopic air pockets that protect against freeze-thaw damage.
