A lot of people think the fridge is cooled by "cold," but it does the opposite -- moving heat from inside to outside. You know how the hot porter works in four stages, and you're never gonna put the fridge in a closed cabinet and block its only vent。
The second law of thermodynamics determines that refrigerators must consume electricity
The calorie is born only from high temperatures to low temperatures and does not run in the opposite direction. The freezer room remained around four degrees, outside the room was 37 degrees in the summer, and the heat was naturally intended to drill into the fridge. On the contrary, the refrigerator has to move heat from the cold to the heat, which has to be done externally, i. E. By plugging in the electric-driven compressor. The second law of thermodynamics speaks of this limitation, and all refrigeration equipment cannot be bypassed。
A sample of 300 refrigerators sold by the national electronics association in mid-2024 showed that a 220-litre double-door refrigerator consumed approximately 0. 7 to 0. 9 degrees per day, more than 70 per cent of which eventually turned to heat in the kitchen or living room. That means the fridge is not just cold inside, it's heating the room. In the summer, the refrigerators were attached to stoves or heating plates, the heat-dispersion routes were blocked, compressors were operating at high loads for long periods, and electricity consumption and noise were significantly increased。
Refrigerants in the evaporation phase heat up inside the fridge
The evaporation unit inside the refrigerator is a low-temperature, low-pressure liquid refrigerant, which is currently the dominant use of r600a isobutane and the old model r134a. These liquid temperatures are lower than the air in the refrigerator, air heat is automatically passed to the liquid, which boils into gas after heating. The surface temperature of the freezer in the freezer is about 5 to 20 degrees below zero, and the water in the food is gradually frozen below 30 degrees below zero。
Contrary to the direction of white gas in the mouth of the winter, water vapour condensates and heats, and evaporaters are liquid heating and gasification. The evaporation unit is usually hidden inside the back of the freezer or in the windway, and it works where you put your hand in the back of the freezer. After the evaporation phase has been completed, the refrigerant changes from liquid to gas and is ready to be carried by compressor to the high-pressure zone for heating。
Compression and condensation keep the heat out. Noodles
The compressor presses the low-pressure gas out of the evaporation unit into a high-pressure state, and the temperature soars to 70 to 80 degrees in an instant, which is equivalent to the heat from the balloon. High-pressure gases follow the copper pipe to the condenser in the back or bottom of the refrigerator, and metal-scattered sheets increase the surface area of the tube several times, the heat is taken away from the surrounding air and the gas is gradually cooled to high-pressure liquids and ready to enter the next throttle。
That's why the back and the bottom of the fridge feel their hands hot. A summer study in shanghai in 2023 found that the kitchen was three to four degrees higher than the room outside the fridge and stove, mainly because of the condenser heat. The cryogenic efficiency of the condenser directly determines the life of the refrigerator, and the manufacturer's instructions repeatedly emphasize that the refrigerator should not be placed in a closed cabinet, leaving at least five centimetres of space on the bottom and back for air circulation。
The swelling valve is the gateway for refrigerants from high to low pressure
High pressure liquid refrigerants from condensers pass through a catheter or electro-inflating valve, and pressure and temperature drop sharply within a few seconds at point zero. For example, from 1. 6 mpa to 0. 2 mpa, the temperature fell directly from 40 degrees to less than 10 degrees, the refrigerant was transformed into a low-temperature liquid and was ready to re-enter the evaporation unit for heating. This step, without mechanical involvement, is based solely on liquid throttle relief to achieve rapid cooling。
The flow control of the expansion valve is critical. Too big for refrigerants to evaporate completely in the evaporation unit and return to the compressor with the gas, which will cause hydraulic damage to the pistons and valves; too small, not enough refrigeration, and no cooling of the refrigerator. The variable-frequency refrigerators use electro-inflating valves to adjust the compressor's variable frequency, allowing them to fine-tune the flow dozens of times per minute, which is much more accurate than the stationary hair tube of the frequency machine and more stable body temperature。
What role each of the five components has to play
The compressor is the heart, and the copper pump structure removes the gas from the low-pressure, high-pressure end. A compressor is designed to have a life of approximately 15,000 hours, with a contract for five to eight years. The condensers are thermal wings, the evaporationers are thermal sponges, the swelling valves are throttle gates, and the polyurethane insulation foams are thermocooled shells. Five components are linked to a closed pipeline in which refrigerants circulate without loss。
The insulation is filled with polyurethane hair bubbles with a conductivity of 0. 02 watts per metre of kelvin, which is more insulated than static air. The new national standard for 2025 requires household refrigerator insulation to be no less than 45 mm thick. The inside fan is responsible for smoothing the cold air over each shelf and avoiding high temperatures in areas close to the door. The freezer room is separated from the freezer room by partition, and the wind route design determines which side is cold and which side is less volatile。
Energy conversionAnd future energy conservation directions
Throughout the cycle, electro-modification mechanically drives compressors, mechanically able to compress gases, which are heated in condensers and inhaled in evaporaters. The total energy remained constant, but the heat was moved outside. The indicator of efficiency is the energy efficiency ratio, with the first-level energy-efficient refrigerators being more than four times more efficient, which means that the amount of heat taken from the four or more degrees of electricity at once is filled by natural heating from the surrounding environment。
In 2025, haile and may presented the prototype of the magnetic refrigeration refrigerator at the ces exhibition, replacing the compressor with alloy materials, using the intersection magnetic field for magnetic inhalation and re-heating of the material, with a laboratory stage energy consumption approximately 30 per cent below that of the traditional compression. At present, however, production costs are more than three times those of traditional programmes and are not used by ordinary households in the short term, and compressed refrigeration remains the absolute mainstream。
Is that metal pipe on the back of your fridge hot in the summer? Welcome to the comment section about your experience, and if you think it's useful, send a compliment to the family who likes to stuff the fridge into a blast。
