Basic Knowledge of Refrigeration and Air Conditioning: You May Not Know It All!

2025-05-06

I. Basic Concepts of Air Conditioners and Refrigerants

Air Conditioner:
An air conditioner, namely an Air Conditioner, refers to equipment that uses artificial means to regulate and control parameters such as the temperature, humidity, and flow rate of the environmental air inside a building or structure.
It generally includes several major parts such as the cold source/heat source equipment, the hot and cold medium transportation and distribution system, terminal devices, etc., and other auxiliary equipment. It mainly includes the refrigeration main unit, water pump, fan, and pipeline system. The terminal devices are responsible for using the supplied cooling and heating amounts to specifically process the air state, so that the air parameters of the target environment meet the requirements.
Two Concepts
Sensible Heat: The increase or decrease of heat does not lead to a change in state and can be measured with a thermometer.
Latent Heat: The heat when the state changes while the temperature or pressure remains unchanged. Latent heat cannot be measured with a thermometer.
Refrigerant
A refrigerant, also known as a refrigerant medium, a refrigerating agent, or a refrigerant gas, is a medium substance that enables the completion of energy conversion in various heat engines.
II. Common Air Conditioning Units and Their Application Places in China
Currently, the common units in China mainly include the following types:
VRV Air Conditioning Unit
Main Application Places: Large-area multi-bedroom apartments, duplex residences, courtyard villas, high-end commercial and residential buildings, unit-style office buildings, etc.
Small Split Units:
Main Application Places: Family households, courtyard villas, conference rooms, small hotels, small and medium-sized restaurants, etc.
Duct Air Conditioning Unit
Main Application Places: Shopping malls, hotel lobbies, large conference rooms, restaurants, canteens, airports, entertainment venues, etc.
Water-based Air Conditioning Unit
Main Application Places: Villas, hospitals, hotels, guesthouses, offices, office buildings, airports, entertainment venues
III. Differences between Inverter Air Conditioners and Ordinary Air Conditioners
The so-called "inverter air conditioner" is a concept that emerged in comparison with the traditional "fixed-frequency air conditioner". As is well known, the grid voltage in China is 220 volts and 50 hertz. An air conditioner operating under such conditions is called a "fixed-frequency air conditioner". Since the power supply frequency cannot be changed, the rotation speed of the compressor of a traditional fixed-frequency air conditioner is basically constant. It adjusts the indoor temperature by continuously "turning on and off" the compressor. The frequent on-off is likely to cause the room temperature to fluctuate between hot and cold and consume more electrical energy.
In contrast, an "inverter air conditioner" changes the power supply frequency of the compressor through an inverter and adjusts the rotation speed of the compressor. It achieves the purpose of controlling the room temperature by relying on the speed of the compressor. The room temperature fluctuates little, the power consumption is low, and the comfort level is greatly improved.

An inverter air conditioner using inverter control technology can automatically select the heating, cooling, and dehumidifying operation modes according to the ambient temperature, enabling the living room to quickly reach the required temperature within a short time and achieve a fast, energy-saving, and comfortable temperature control effect with small temperature difference fluctuations in a low-speed and low-energy-consumption state.
When the power supply frequency is high, the compressor rotates quickly, and the cooling (heating) capacity of the air conditioner is large; when the power supply frequency is low, the cooling (heating) capacity of the air conditioner is small. This is the so-called "inverter" principle. The core of an inverter air conditioner is its inverter, which realizes the automatic adjustment of the motor's operating frequency through the conversion of current, changing the fixed grid frequency of 50Hz to a variable frequency ranging from 30 to 130Hz. At the same time, it also expands the power supply voltage range to 142V to 270V, completely solving the problem that the air conditioner cannot work properly due to the instability of the grid voltage.
When an inverter air conditioner is first used each time, it usually allows the air conditioner to operate at the maximum power and maximum air volume for heating or cooling to quickly approach the set temperature. Since the inverter air conditioner does this by increasing the working frequency of the compressor.
When the indoor fan of an inverter air conditioner runs automatically, the rotation speed will change within the range of 12 wind speed gears according to the working frequency of the compressor. Since the rotation speed of the fan is reasonably matched with the capacity of the air conditioner, it achieves quiet operation with low noise. When the air conditioner operates at high power and quickly approaches the set temperature, the compressor will operate at a low speed and low energy consumption state, maintaining the set temperature with only the required power. In this way, not only is the temperature stable, but it also avoids the reduction in the service life caused by the frequent on-off of the compressor, and the power consumption is greatly reduced, achieving high efficiency and energy saving.
The Working Principle of the VRV Inverter Air Conditioning Unit
A multi-split unit uses a high-power outdoor main unit to drive multiple indoor units. Since it adopts a parallel connection method, it can be conveniently used for zonal control. The medium for transporting energy is the refrigerant, and small copper pipes can be used to replace large air ducts, and the noise is also greatly reduced. Since the refrigerant distribution technology and electrical control technology require a high level, and the parts are highly specialized.
The Main Structure of Small Split Units
IV. Commonly Used Tools in Daily Air Conditioner Maintenance:
Pressure Gauge: Refrigerant leakage is a common fault of air conditioners. To detect whether the amount of refrigerant in the system is sufficient, a pressure gauge is commonly used. A pressure gauge is a commonly used detection tool in the Freon refrigeration system. It can be used to evacuate the refrigeration system, charge the refrigerant, and test the pressure, etc.
Pipe Expander: The function of the pipe expander is to expand copper pipes of different specifications as needed. When expanding the pipe, first put the annealed copper pipe into the corresponding aperture of the pipe wrench. The length of the copper pipe extending out of the pipe wrench varies with the diameter of the pipe.
Flaring Tool: The flaring tool is used to flare the copper pipe into a bell mouth so that the indoor and outdoor units of the split air conditioner can be connected through the piping. When flaring, first put the annealed copper pipe through the connecting nut, and then put the copper pipe into the corresponding aperture of the pipe wrench.
Cutter: When cutting the copper pipe, the copper pipe must be placed between the two rollers of the pipe cutter. Rotate the feed knob clockwise to clamp the copper pipe between the cutter and the rollers. Then, while rotating the feed knob, rotate the pipe cutter around the copper pipe. When rotating the feed knob, the force must be uniform and gentle; otherwise, the copper pipe may be squeezed and deformed.
Pipe Bender: The pipe bender is a tool used to change the shape of the copper pipe and process the copper pipe into the required shape. There are various sizes of pipe benders, suitable for bending copper pipes with a radius of less than 20mm. When bending the pipe, first put the annealed copper pipe into the wheel groove of the pipe bender, lock the pipe clamping hook, and slowly rotate the handle until the required angle is reached.
Welding Torch: The refrigeration system of an air conditioner mostly uses copper pipes, and gas welding is required during maintenance. The gas welding equipment uses a mixture of oxygen and acetylene gas, and a high-temperature flame is generated after ignition.
There are many commonly used tools for air conditioner maintenance, and only some of them are listed above.
V.
Commonly Used Unit Conversions in Air Conditioner Maintenance
Energy = Work × Time
1 Joule (j) = 1 Watt (W) × 1 Second (s)
(1) Energy Units:
Metric System: j, kj; British System: cal, kcal
1j = 0.2388cal
(2) Energy Units:
Metric System: w, kw; British System: kcal/h (kilo-calorie)
1kcal/h = 1.163w
1kw = 860kcal/h
Commonly Used Units in Habit: Horsepower (HP), Refrigeration Ton (RT)
1HP = 735w
1RT = 3.516kw = 3024kcal/h
Explanation:
Refrigeration Ton: It is a British unit of refrigeration.
1 refrigeration ton is the cooling capacity required to freeze 1 ton of water at 0°C into ice at 0°C within 24 hours.
The United States uses 2000 pounds (907.2kg) as one ton.
Therefore, 1 US refrigeration ton = 12659kj/h; that is, 1RT = 3.516kw
The Relationship between Horsepower and Refrigeration Capacity
In small air conditioning projects, 1HP refers to the refrigeration capacity generated by inputting 735w of power to the compressor. It has a different meaning from the general power unit of horsepower. Here, 1HP is calculated based on the energy efficiency ratio.
In Japan, it is generally believed that the average energy efficiency ratio of an air conditioner compressor is 3.4, so the refrigeration capacity generated by inputting 735w of electrical energy is 2500w. Therefore, it can be said that the refrigeration capacity of a 1HP air conditioner is equivalent to that of 2500w. A small 1HP is generally 2200W, and a large 1HP is generally 2800W.
Calculation Formula and Case
Under normal circumstances, the required refrigeration capacity per square meter of an ordinary family room is 115-145W, the required refrigeration capacity per square meter of the living room and dining room is 145-175W, and the refrigeration capacity of the air conditioner in a conference or training room is (350-450W/㎡)
For example: The usable area of a family living room is 15 square meters. If calculated based on the required refrigeration capacity of 160W per square meter, the required air conditioning refrigeration capacity is: 160W × 15 = 2400W. In this way, you can select and purchase a KF-25GW split air conditioner with a refrigeration capacity of 2500W corresponding to the required 2400W of refrigeration capacity.
If it is a shopping mall or an office building, many external factors such as (equipment load, lighting load, building maintenance structure load, supplementary fresh air load, heat dissipation load of personnel, and others) need to be considered. The formula Q_total = Q1 + Q2 + Q3 + Q4 + Q5 can be used for calculation. For example, to calculate the required refrigeration capacity of a large shopping mall or a large office building, it is: Q_total + the refrigeration capacity required for the area.