How does A Bus Air Conditioning System work? (Wikipedia)

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Jan 30,

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A bus air conditioning system, also known as an HVAC (heating, ventilation, and air conditioning) system, is designed to provide comfort and maintain a pleasant temperature for passengers during both hot and cold weather conditions. The system typically consists of several major components: the compressor, condenser, evaporator, expansion valve or orifice tube, refrigerant, and electrical controls.

The Compressor

The compressor is the heart of the air conditioning system. It&#;s responsible for circulating the refrigerant throughout the entire system. When the thermostat signals that cooling is required, the compressor pressurizes and pumps low-pressure refrigerant vapor into the condenser. This component is usually driven by a belt connected to the engine, but some newer systems use electrically powered compressors.

The Condenser

After leaving the compressor, high-pressure, high-temperature refrigerant gas enters the condenser. Here, heat from the refrigerant is transferred to the outside environment with help from ambient air passing through fins surrounding tubes carrying the heated refrigerant. As this process continues, the refrigerant changes state from a gas to a liquid due to decreased temperature and increased pressure. Once cooled sufficiently, it moves on to the next stage.

The Evaporator

Following the condenser, the now cooler liquid refrigerant travels through an expansion device &#; either an expansion valve or orifice tube &#; which regulates the flow of refrigerant into the evaporator coil. Inside the evaporator, warm cabin air comes into contact with the chilled refrigerant causing it to absorb heat energy. Simultaneously, moisture from the humid air condenses onto the cold surface of the evaporator creating a dehumidifying effect inside the vehicle. After absorbing enough heat, the refrigerant turns back into a low-pressure vapor, ready to return to the compressor to repeat the cycle.

Expansion Valve vs Orifice Tube

Both devices serve similar purposes; they control the amount of liquid refrigerant entering the evaporator. However, their operation methods differ slightly. An expansion valve uses a diaphragm controlled by a bulb filled with refrigerant from the outlet of the evaporator. As the temperature drops at the end of the evaporator, less refrigerant flows through the valve, maintaining optimal superheat levels within the evaporator. On the other hand, an orifice tube maintains a constant restriction regardless of changing operating conditions, relying on a metering rod to adjust flow based on pressure difference across the two sides of the orrifice. While simpler in design, orifice tubes can be less efficient than expansion valves under varying load conditions.

Refrigerants

Refrigerants are critical to the functioning of any AC system. They have unique properties allowing them to change phase easily when subjected to different temperatures and pressures. Older systems used R-12 (Freon), but environmental concerns led to its phasing out. Modern systems primarily utilize R-134a, although new generations of lower global warming potential refrigerants like R-407C and R-410A are becoming more common.

Electrical Controls

Various sensors and switches monitor system performance and ensure proper functionality. Key among these are the temperature sensor, which measures interior temperature and sends feedback to the control module, and the pressure switch, which safeguards against excessive system pressure. Additionally, climate control panels allow occupants to select desired settings such as fan speed, mode (e.g., floor, dashboard, defrost), and temperature. These inputs are processed by the electronic control unit (ECU), which manages operations accordingly.

Conclusion

In summary, a bus air conditioning system relies on multiple interconnected components working together harmoniously to deliver comfortable temperatures for passengers despite external weather conditions. Through continuous circulation, compression, condensation, evaporation, and expansion of refrigerant, along with precise regulation via various sensors and controls, these sophisticated systems significantly enhance travel experiences.
TKT has a large factory engaged in the production and sales of bus air conditioners for more than 20 + years. We specialize in producing Bus A/C, RV A/C, Parking A/C, BTMS systems and DC Charging Piles. We provide design and technical support to the world&#;s leading OEMs, including BYD, Tata Motors, Switch Mobility, and more than 150 other outstanding companies. Welcome to contact us.

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This article will introduce in detail some information about bus air conditioning unit. Include the following contents respectively:
1 What type of AC is used in buses?
2 Installation steps of bus air conditioning unit
3 What is bus air conditioning unit?
4 How does the HVAC system work on a bus?
5 What does an AC bus do?

What type of AC is used in buses?

I'll start with the bus model. First of all, the most common diesel bus. It usually uses an engine-driven bus air conditioning unit. This type of air conditioning unit has a high cooling capacity and is cost-effective. The disadvantage is that it cannot use when parked. If you need to use it when parking, we recommend choosing Sub Engine Bus Air Conditioning (but relatively expensive).

Let me add another special case - mini bus. This kind of bus can choose 1 or 2 12v/24v mini bus air conditioning unit. This solution has a relatively low cooling capacity and is suitable for areas and countries that are not very hot.

Followed by the new electric buses. This kind of bus uses high-voltage power battery as energy source. They have high battery capacity and can be used for electric bus air conditioning. Whether it is cooling capacity or parking use, it can easily meet your needs.

TKT HVAC busthermo is one of the top 3 bus air conditioner manufacturers in China. Founded in , it has rich OEM customization experience and production experience. We have a variety of solutions that are sure to solve your coach cooling problems. Welcome to leave a message to communicate.

Installation steps of bus air conditioning unit

Air conditioning unit part

1. Opening: Check that the bus roof opening should be consistent with the opening size of the air conditioner.
2. Cleaning: Clean the car roof to ensure it is clean and tidy.
3. Sealing: Apply sealing insulation sponge around the roof air outlet and return air outlet, and ensure sealing.
4. Fixing: Find the corresponding positions of all bolts and shock-absorbing rubber pads, and use sealant to fix them.
5. Installation: Hoist the bus air conditioning unit. After finding the installation location, use the corresponding mounting holes and bolts to secure it firmly. Then apply sealant again to strengthen the fixation.
6. Interior: Check the interior of the bus to see if the sealing insulation sponges on the air outlet and return air outlet are compacted and sealed. Then apply sealant evenly, with a thickness of not less than 3MM. To strengthen fixation and sealing.
7. Cleaning: After all work is completed, clean the inside of the bus air conditioning unit and install the top cover correctly on the roof unit.

Pipe installation (drainage pipes, refrigeration system pipes)

1. The evaporation chamber of the air conditioner has drainage holes. After connecting the drainage hose, fix the pipe in the air ducts on both sides of the roof and lead it to the outside of the car. During the installation process, attention should be paid to ensuring that the water pipes are not compressed and prevented from coming into contact with sharp objects.

2. To install the refrigeration pipeline, first slowly loosen the blockage at the joint between the evaporator and the condenser to allow the precharged dry nitrogen to overflow. Then connect the refrigeration pipeline to the evaporator and condenser correspondingly. Apply refrigeration oil to the sealing ring, spreading it evenly to ensure good contact.

Compressor installation

Fix the compressor on the bus chassis, tighten the bolts, adjust the shock absorber spring, and fix the compressor clutch on the compressor bracket. Then connect the drive belt of the compressor to the bus engine, making sure it is tight. Other pipeline parts are fixed with clamps and must be kept away from heat sources and sharp objects to ensure heat dissipation and longevity as much as possible.

Final inspection

1. Pour in nitrogen to maintain pressure to check the tightness of the refrigeration system, and finally fill it with refrigerant.
2. Check all connections to make sure they are installed correctly and tight.
3. Start the air conditioning system and check its operation. Listen carefully for abnormal noise and check for abnormal vibration.
4. After running the system for a while, check the pressure and temperature again to make sure they are within the normal range.
5. Finally, perform a thorough cleaning and inspection to ensure that all work has been completed and no parts have been missed.

What is bus air conditioning unit?

Bus air conditioning unit is the air conditioner installed on the bus. Its principle is similar to that of home air conditioners, but bus air conditioning also need to consider the driving status and bumps of the vehicle. Therefore, it needs to adopt more stable and reliable refrigeration technology and materials. It is very important for passenger comfort experience.

Bus air conditioner is mainly composed of compressor, condenser, evaporator, piping system and electronic control system. Usually the condenser and evaporator are installed on the roof of the bus. The liquid reservoir, dry filter and expansion valve are installed inside the evaporator. The air conditioner controller is installed on the dashboard.

Bus air conditioning unit condenser:

The condenser is a heat exchange device that condenses the high-pressure and high-temperature refrigerant gas discharged from the compressor into a liquid state after releasing heat through it.

Specifically, in the condenser it is the refrigerant that transfers heat to the surrounding ambient air. The refrigerant flows in the tube. During the heat release process, the refrigerant gas gradually condenses into a refrigerant liquid, and the external ambient air absorbs heat and becomes hot. The air blown by the condensing fan dissipates heat efficiently.

Bus air conditioning unit evaporator:

The evaporator is a device that absorbs heat and vaporizes the refrigerant that has been throttled by the expansion valve to achieve the cooling effect.

Specifically, when the air passes through the evaporator core, heat is taken away by the refrigerant in the core, thereby cooling the air. In order to prevent water droplets from condensing on the evaporator core and being carried into the cabin by the air flow, the outer surface of the evaporator core is coated with a hydrophilic film.

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How does the HVAC system work on a bus?

The work of the bus air conditioning unit is divided into four processes.

A. Compression process: It absorbs heat in the evaporator and turns it into a low-temperature and low-pressure gaseous refrigerant. After being sucked and compressed by the compressor, it turns into a high-temperature and high-pressure gaseous refrigerant and is discharged into the condenser.

B. Condensation process: After the high-temperature and high-pressure gaseous refrigerant enters the condenser, it dissipates heat to the surrounding ambient air through the condenser radiator under the action of the condenser fan, and at the same time condenses into high-temperature and high-pressure liquid refrigerant.

C. Throttling process: After the high-temperature and high-pressure liquid refrigerant passes through the liquid receiver and filter dryer, it is throttled to cool down and depressurize through the expansion valve, and becomes a mixture of low-temperature and low-pressure liquid and gaseous refrigerant and enters the evaporator.

D. Evaporation process: The refrigerant is throttled by the expansion valve and becomes a mixture of low-temperature and low-pressure liquid and gaseous state. It vaporizes in the evaporator. Under the action of the evaporator fan, it absorbs the heat of the air in the cabin to cool the air in the cabin, and at the same time precipitates condensation. water. After absorbing heat, the refrigerant evaporates into low-temperature and low-pressure gaseous refrigerant, which is sucked into the compressor and then compressed to complete a refrigeration cycle.

The compressor keeps running, the above-mentioned refrigeration process circulates continuously, and the heat in the bus is continuously taken away by the refrigerant in the evaporator, thereby completing the cooling of the bus.

What does an AC bus do?

Mainly reflected in the following aspects:

1. Improve the air quality in the bus: The air conditioner can circulate fresh air, discharge the dirty air in the bus, reduce dust, carbon dioxide, bacteria and other harmful substances, and provide passengers with a fresh environment.

2. Improve passenger comfort: In hot summer, air conditioning can control the temperature inside the bus at a temperature that is comfortable for the human body, thereby improving the passenger riding experience.

3. Energy saving and environmental protection: With the development of new energy buses, the design of air conditioning systems is more energy-saving and environmentally friendly, which can effectively reduce energy consumption and reduce the impact on the environment.

TKT Bus Air Conditioner

TKT was established in . TKT HVAC has advanced cooling technology and manufacturing processes to further improve refrigeration and heat transfer efficiency. If you care about energy saving and environmental protection, we are your best choice.

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Contact us to discuss your requirements of tourist bus air conditioner. Our experienced sales team can help you identify the options that best suit your needs.