An air-cooled chiller is the most important part of central air conditioning systems, and it comes in various sizes and capacities. Stay with us to learn about the types, components, and capacity estimation for choosing the air-cooled chillers.
A Guide to Choosing Different Types of Air-Cooled Chillers
Air-cooled chillers are utilized in air conditioning systems to provide cold water, typically between 7 to 12 degrees Celsius, or in industrial refrigeration systems through the condensation refrigeration cycle. Air-cooled chillers are used as the beating heart of the building's cooling system, where water cooling towers and water-cooled chillers are not usable because of high relative humidity (RH). The mechanism of the air-cooled chillers (usually installed in open spaces such as the roof of the building) is based on the condensation refrigeration cycle, similar to the water-cooled chillers.
The Main Parts of an Air-Cooled Chiller
Air-cooled chillers usually contain four main parts, which are as follows:
Compressor
Condenser
Evaporator
Expansion valve
Capacity Calculation of an Air-Cooled Chiller
Before we start, let us inform you that the "nominal capacity" and the "actual capacity" of an air-cooled chiller is the most important thing to keep in mind when choosing the Air-cooled chiller, considering the average temperature (outdoor temperature) of the hottest days in summer of the operating area. Also, consider the sufficient heat exchanger levels in "the condenser" and "evaporator", length, diameter, and the number of tubes used in the condenser as one the important factors in the performance of the actual capacity of an air-cooled chiller. To calculate the required air chiller capacity (phase 1 electricity) for residential and office buildings in cities like Tehran, Isfahan, Shiraz, Mashhad, Semnan, Shahroud, Karaj, Kermanshah, Arak, Sulaimaniyah, Kirkuk, Mosul, Erbil, Aleppo, Damascus, Beirut, and Kabul, consider 1 ton of refrigeration capacity for every 30 square meters of usable building infrastructure.
In hot and humid climates such as Ahvaz, Abadan, Mahshahr, Bandar Abbas, Kish, Chabahar, Basra, Karachi, Dubai, Sharjah, Muscat, Abu Dhabi, Jeddah, Sana'a, and Doha, an additional 20 to 30% cooling capacity is required for air-cooled chillers, according to the project facility expert's calculations and HVAC calculation software. Also, before finalizing the capacity calculation of the chiller, contact the experts of DamaTajhiz HVAC Group to choose the right capacity of the required device for the project. Our experts are always ready to answer you.
Factors to Consider When Choosing the Right Capacity for an Air-Cooled Chiller
Consider the volume of cold water needed and the reliability coefficients necessary for efficient chiller operation. Generally, facility experts determine the air-cooled chiller capacity required for each project by calculating the total cooling load capacity and considering various factors you should also consider. Factors such as:
Geographical conditions
Ambient temperature and altitude from sea level
Relative air humidity
Building usage (interior temperature)
Buildings materials
Facade design
Building orientation relative to the sun
Number of floors
The building's substructure level
The number of occupants and electrical equipment inside the building
Refrigeration Cycle in Air-Cooled Chillers Explained
First, condensed gas with high pressure and temperature enters the condenser, cooled by the ambient air (forced-blown air of the fan), and turns into a liquid at the lower section of the condenser. Then, this liquid is cooled down by passing through the expansion valve or the capillary tube, which is the sudden drop in liquid pressure so that it can absorb the heat of the water inside the evaporator after entering the evaporator coil so that the refrigerant liquid can absorb the heat from the water then evaporates. As a result, the water in the refrigeration system is cooled inside the evaporator. Then transferred by the circulator pump system to the fan coil units and air conditioners to create cool air in the selected location. After the compressor's suction, due to the evaporation of the refrigerant, it moves toward the compressor in the evaporator, and the cycle repeats.
Air-Cooled Chiller Circuit Information
The operating temperature of a chiller in air conditioning systems refers to the temperature of the chilled water exiting the evaporator. This temperature should not fall below 7 degrees Celsius (44.6 degrees Fahrenheit). Also, the temperature of the water returning to the evaporator should be approximately 5 degrees Celsius (9 degrees Fahrenheit) warmer than the water coming out of the evaporator. Additionally, it is crucial to remember that the standard set temperature for the antifreeze thermostat is typically 4 degrees Celsius (39.2 degrees Fahrenheit).
Air-Cooled Chiller Multi-Stage Thermostat and the Unloader:
Using a 3-stage or 4-stage thermostat based on the type of chiller, the number of compressors, the number of air chiller circuits, or even the unloader system that is installed on the output water of the evaporator can increase the performance according to the set temperatures on the gradual thermostat. Installing the unloader system in the compressor of the air-cooled chiller can save and reduce electricity consumption by reducing the refrigeration load. The unloader mechanism is used to reduce the pressure load during start-up and the capacity control during use in a way that is completely proportional to the amount of refrigeration required, which increases the life of the device and its efficiency compared to other systems. Moreover, significantly reduces the cost of electricity, maintenance, and repair. Unloading the compressor in proportion to reducing the system load reduces the input power to the compressor. It reduces the stress on the engine and compressor, which is caused by the number of times the device is turned on and off.
4 Technical Information About Air-Cooled Chillers
There is much technical information to mind when choosing an air-cooled chiller, but here are 4 of the most important ones:
Free cooling in air-cooled chillers
Superheat refrigerant in the suction line of the compression chiller
Subcool in Subcool compression chiller condenser
Pump down compression chiller Pump Down
Air-Cooled Chiller Compressor Types
When choosing an air-cooled chiller or any other chiller, it is essential to mind not only the type of compressor (screw, scroll, reciprocating, etc.) but also the number, capacity, and brand, as these are some of the main components of chillers. Compressors used in air-cooled chillers have several types based on refrigerant gas compression mechanisms. These compressors can be categorized into the following groups:
Reciprocating or piston compressors (reciprocating)
Screw compressors (Screw)
Spiral compressors (Scroll)
Rotary compressors (Rotary)
Centrifugal compressors
The operating principle of the first four compressors, "positive displacement", significantly differs from centrifugal (dynamic) compressors. In "positive displacement" compressors, a certain volume of gas is constantly reduced by the piston, spiral, or rotation, and as the gas volume decreases, the vapor pressure increases. In centrifugal compressors, the refrigerant gas is compressed due to acceleration by the rotating propeller, and its pressure increases as the speed decreases in a diffuser.
Note: Centrifugal compressors are used in very high capacities.
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Different Types of Compressors Based on the Housing & the Electric Motor
In terms of the connection between the compressor housing and the electric motor, compressors are divided into the following three categories:
Closed-Type Compressor (Hermetic): In closed compressors, the electric motor and compressor housing share a single shell, making repairs impossible in case of damage. These compressors typically have a smaller capacity.
Open-Type compressor: Open-type compressors have separate compressor housings and electro-motor components connected by a coupling, and these compressors are designed for high-capacity applications.
Semi-Hermetic compressor: Semi-hermetic compressors feature a two-part shell, with the motors and electro-motors in separate compartments. The engine and compressor parts are completely visible, and these compressors have a higher capacity than closed compressors.
Buying an Air-Cooled Chiller
Before discussing the price of the air-cooled chillers and accompanying equipment like fan coils, it's essential to understand the installation site's climate and weather conditions, the cooling capacity, maximum cold water flow, and required water pressure.
When buying an air-cooled chiller, it is essential to understand the installation site's climate and weather conditions, the cooling capacity, maximum cold water flow, and required water pressure.
The DamaTajhiz HVAC website provides technical information for numerous air-cooled chiller models from reputed brands with their main guarantee, allowing you to make informed and smart buying decisions.
Air Cooled Chillers Prices
There are various useful factors concerning the price of both buying and installing an air-cooled chiller; the most important one is the type of capacity and technical specifications, the type and brand of the selected chiller equipment. The installation cost of an air-cooled chiller differs based on the project's capacity, specific conditions, and workers' expenses. All the air-cooled chillers presented on the website of DamaTajhiz HVAC Group have product IDs and reasonable prices, and the discounts are already included.
Air-Cooled Chiller Condenser Overview
A condenser is a heat exchanger that transfers heat from the refrigerant gas to the air. Condensers used in air-cooled chillers are cooled down via air. The device condenser comprises copper tubes (for refrigerant liquid flow) and aluminum fins (for air passage and heat transfer).
Comparison table of how air-cooled and water-cooled condensers work
Air-cooled condenser
Cooled water condenser
More power consumption
Less power consumption
No need to use water
High water consumption
Suitable in most climates and weather conditions
Restrictions in less climatic conditions (hot and dry)
Higher starting price
Lower initial price
No need for water pumps
The need for cooling tower water circulation pumps
It has a lower performance factor
Higher coefficient of performance (higher COP)
Installing the device outdoors
Installation of the device in the central engine room
Simple maintenance conditions (no need for acid washing and sedimentation)
Complex maintenance conditions (requires sedimentation and acid washing)
Larger dimensions
Smaller dimensions
Air-cooled Chiller Condenser Types
Typically, there are three types of condensers:
Air-Cooled Condenser: In air-cooled condensers, the air is used as a cooling agent and refrigerant distillation.
Water-Cooled Condenser (double-tube, shell, and coil, shell and tube condensers): In water-cooled condensers, water is used as a cooling agent and refrigerant distillation instead of air.
Evaporative Condenser: In evaporative condensers, both air and water are used. Although in evaporative condensers, the temperature of the passing air increases a little, the distillation of the refrigerant is mainly caused by the evaporation of the water sprayed on the condenser. The result from the evaporation, which is mainly used in the first type of air-cooled chiller task of the air is to increase the intensity of the evaporation by removing the water vapor
Airflow in air-cooled condensers can be done in the following two ways: 1. Natural and without ventilation fans such as refrigerators and freezers. 2. Airflow by fan or ventilation (forced airflow)
Expansion Valve in the Refrigeration Cycle of the Air-Cooled Chiller
The expansion valve in all air-cooled chillers causes a sudden drop in pressure in the path of the refrigerant gas passing to the evaporator, causing the refrigerant gas to change from hot into cold refrigerant. The expansion valve in an air-cooled chiller can be designed as mechanical, thermostatic, or electronic. Electronic expansion valves are used in high-capacity chillers to provide enhanced and precise management and control of the output water temperature.
Types of Evaporators in Air-Cooled Chillers
The expansion valve in all air-cooled chillers causes a sudden drop in pressure in the path of the refrigerant passing to the evaporator, causing the refrigerant to change from hot liquid to cold refrigerant. The expansion valve in a chiller can be designed as mechanical, thermostatic, or electronic. Electronic expansion valves are utilized in high-capacity chillers to provide enhanced and precise management and control of the outlet water temperature.
Shell and Tube evaporator
In this type of evaporator, parallel horizontal tubes are embedded in a very strong steel shell, usually the liquid fluid (refrigerant) inside the tubes and the water circulating in the air conditioning system or industrial cycle around the tube (inside the shell). With the exchange of heat between the liquid fluid inside the pipes and the water inside the shell, the water temperature decreases and cools, and on the other hand, the liquid fluid changes its phase and turns into a gas by absorbing heat from the water.
Plate evaporator
These evaporators consist of metal plates, which are placed together, and two fluids without physical contact with each other are created from a distance and pass between these plates, which are completely sealed to each other, and exchange heat with each other. These evaporators are used in special applications and conditions.
Evaporator with fan or DX
In this type of evaporator, the refrigerant passes through winding pipes, and the air flows around the pipes by a fan. For this reason, it is called an air evaporator with a fan. The fluid inside the tube cools the air volume by taking heat from the air passing through the tubes and directing it to the desired location.
Manufacturing Order & Guarantee of Air-Cooled Chillers
At the DamaTajhiz HVAC Group, we offer various air-cooled chillers from various brands with main guarantees. Our selection is designed to meet the needs of professionals and engineers, providing an easy and suitable buying experience. As a leading supplier of air-cooled chillers in the Middle East region, you can easily place your order for any country within the area. Our sales experts ensure the main product guarantee and competitive pricing, giving you peace of mind throughout buying.
(DamaTajhiz HVAC Group started its activity in 2013 and has an electronic trust symbol.)
1Ton of Ref.=12000 B.T.U. = 3.516 Kw 1Gal. (am.)= 3.785 Lit 1K.Cal = 4 B.T.U C = 1.8 ˚F ˚F= 9/5 ˚C + 32 Kw X 860 = K.Cal
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The first and most reputable company in the nation in the area of building facilities equipment and all air conditioning devices, the specialized collection (DamaTajhiz HVAC Group) provides you with all varieties of sand filters as well as hundreds of other products, all of which are original, have a valid warranty, and are reasonably priced. Additionally, you can get free guidance from the experts in heating equipment if you have any concerns about selecting and contrasting the brands of this product.
Since 2004, DamaTajhiz HVAC Group has been Iran's first and most well-known specialized organization in air conditioners, installation equipment, and all equipment for swimming pools, saunas, and jacuzzis. Use this group's period as a reference. Call +98 21 88822550 to speak with DamaTajhiz HVAC Engineering and Production Company specialists for more information.
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