Final answer:
The defrost cycle in refrigeration systems is initiated by time and temperature, which helps maintain efficiency by preventing unnecessary operation. In well-insulated Northern European homes, warmth is retained even without occupants, thanks to the insulation and other heat sources. Refrigeration systems have better COP and operate more cost-effectively when the temperature difference between the hot and cold sides is minimal.
Step-by-step explanation:
The defrost cycle in refrigeration systems such as those found in refrigerators, air conditioners, and heat pumps is initiated by time and temperature. These two factors work in conjunction to ensure the defrost cycle operates efficiently, removing ice build-up without running unnecessarily.
In Northern European nations where homes are built without traditional heating systems, they rely on excellent insulation and the body heat of residents to maintain warmth. When residents are away, the insulation keeps the house warm by preventing the escape of heat within the home. Solar gain, residual heat from appliances, and passive heating can also contribute to the indoor temperature.
The efficiency of refrigerators, air conditioners, and heat pumps is highly dependent on the temperature difference between the hot side (Th) and the cold side (Tc). Systems operate more cost-effectively with a small temperature difference because the Coefficient of Performance (COP) is better when the energy transfer occurs over a smaller temperature gradient, leading to less energy consumption and more efficient operation.