HVAC COOLING SYSTEM DESIGN

HVAC COOLING SYSTEM DESIGN

 Cooling and heat dissipation techniques are extremely important topics when it comes to designing and operating a data center. In many instances, system designs fall short of clients’ expectations in terms of reliability and availability. Perhaps naively, often too much importance is placed on the power and network availability without the same being applied to the air conditioning systems.

 Remember, ‘a chain is only as strong as its weakest link’. Infrastructure designs often fail to meet expectations because the same level of reliability/redundancy in many instances is not applied to all other components of the supporting infrastructure. While many people understand that only a short interruption in power supply to computer equipment can mean loss of data, what is often not considered is that an interruption in cooling system can be just as devastating.

This section includes:

1. Heat gains

2. Temperature and humidity requirements

3. Ventilation rates

4. Air quality

5. Cooling loads

6. HVAC equipment

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Condenser, Evaporator, and Compressor

Condenser, Evaporator, and Compressor

The condenser is one of three primary elements in your air conditioning system. The other two, the evaporator and compressor, are also important. To understand how the condenser works, it’s important to understand the other two as well.

• Evaporator: The system starts in home with inside air being blown over evaporator coils. These coils contain low-pressure refrigerant which absorbs the heat from the air and converts into a high-pressure gas.
• Compressor: The gas is transferred into the compressor, which is in the outside unit. Here, it’s compressed to help convert it back into a liquid so it can continue the cooling cycle. This produces extra heat.
• Condenser: The condenser is a set of coils, also located inside the outdoor unit. Here, a fan blows across the coils, dissipating the heat from the refrigerant inside them and allowing it to convert back into a liquid, at which point it’s sent back inside to start the process over again.

Without the condenser, the refrigerant would retain its heat and the process would not work. Therefore, it’s important to be able to tell if the condenser is malfunctioning or broken.


Diagnosing Condenser Problems

Often, the problem may not be with the condenser coils themselves, but with the fan or motor in the outdoor unit. The following signs can let you know if the condenser is broken:

• Air conditioner blows warm air inside.
• Outdoor condenser fan doesn’t run.
• Refrigerant leaks from outdoor unit.

Compressor Types

Compressor Types

Two types of compressor dominate HVAC systems in buildings: piston and scroll.
The piston type uses pistons attached to a motor-driven crankshaft to draw in and compress the refrigerant.

Scroll compressors use an orbiting scroll on an eccentric motor-driven crankshaft to suck in vaporized refrigerant and push it into a stationary scroll whose volume gradually decreases to compress the refrigerant. There are three forms of compressor construction. Hermetically sealed units have motor and compressor sealed within a welded steel casing. They can't leak, but they also can't be repaired. Semi-hermetic units put motor and compressor inside a steel shell whose halves are sealed with a gasket and bolts. These can be opened for repairs, but might leak refrigerant. Open compressors have motor and compressor as separate units linked by a coupling. This variety is found in very large HVAC systems.

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What Is the Function of a Compressor in an HVAC System?

What Is the Function of a Compressor in an HVAC System?

The compressor is the heart of the cooling function of heating, ventilation and air conditioning (HVAC) systems. The air conditioner component of a building's HVAC system essentially is a type of refrigerator that cools and dehumidifies the air in the building, ensuring thermal comfort for the occupants. Most HVAC compressors look like a black box with lines running to and from it.

Compressor Function
Air conditioners are devices that transfer heat from an enclosed space to the outside air. The motor-driven compressor in an air conditioning system powers the whole heat-transfer cycle. Air conditioners rely on two facts of nature. One is that heat flows from a high-temperature area to a lower temperature area. The other is that gases always flow from a high-pressure area to a low-pressure area.
Air Conditioning Cycle
The heat-transfer cycle starts as the compressor squeezes the refrigerant. This squeezing action raises its temperature well above that of the surrounding atmosphere. The squeezing action also pressurizes the refrigerant just to its liquefying point so it can flow through the system. The hot, pressurized, liquified refrigerant flows to a condenser coil where it gives up its excess heat to the cooler atmosphere. Typically, a fan blows air through the condenser coil to facilitate transfer of the excess heat.
Expansion Phase
After shedding its excess heat to the atmosphere, the refrigerant flows to an evaporator coil where it expands into a gas at the reduced pressure in the evaporator, which is located in the space to be cooled. This expansion requires heat, which is drawn from the air in the enclosed space that's being cooled. This warms the refrigerant. The cold evaporator also draws humidity from the air. A fan blowing across the evaporator coil facilitates this transfer of heat and humidity. As the compressor pushes hot pressurized refrigerant toward the condenser, it pulls the warm vaporized refrigerant from the evaporator to start the cycle all over again.

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Types of compressors

Types of compressors
The compressor is the component at the heart of a refrigerant circuit based on the so called “vapour compression cycle”.

This thermodynamic cycle exploits the evaporation of a refrigerant inside a closed loop piping circuit.
Specifically, evaporation occurs in a heat exchanger called the evaporator, which absorbs energy from the surrounding air; this is then delivered to the food storage compartment or air-conditioned space by natural or fan-forced convection.
The same also applies when using water as the medium, which is pumped through the heat exchanger and then flows into the storage tank for use by the terminal units.
Once having evaporated, the refrigerant can no longer absorb considerable amounts of energy, and consequently it needs to be returned to the liquid state by condensation.
The problem thus arises of having an environment that’s “cold” enough to absorb energy from the refrigerant, which naturally cannot be the same compartment or space that’s just been cooled.
The compressor is then used to compress the refrigerant to a pressure that’s higher than in the evaporator (up to 8-10 times!) so that the condensation process can take place at a temperature that’s compatible with a readily available “cold” source, typically the outside air.
Condensation thus occurs at a high temperature (usually 35-55°C) inside a heat exchanger where the two fluids are outside air and refrigerant. The latter condenses and returns to the liquid state, while the outside air will be heated. The liquid refrigerant is still at high pressure when it leaves the condenser. An expansion device is thus needed to expand the liquid refrigerant and reduce its pressure to the value at which evaporation occurs. The refrigerant has now returned to its initial state (liquid at low pressure and temperature) and can once again absorb energy from the air or water.

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HVAC Components

HVAC Components
Other important components of an HVAC system include:
Ductwork: This system of metal pathways allows for distribution of hot or cold air throughout your home.
Humidifier: Adds moisture back into the air before distribution throughout the home, ultimately making breathing easier.
Thermostat: This is what allows you to control the temperature in your home.
Filters: Ensures air in your home is free of dirt, allergens, and odors, and helps maintain your system.
In order to ensure that all aspects of your home’s HVAC system are running at peak performance, it is essential to perform seasonal and annual maintenance. Keeping filters and ducts clean of dust and debris helps make your system more efficient. It also ensures your HVAC systems keeps your family comfortable for many years.

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How Does HVAC Work?

How Does HVAC Work?

Understanding Heating, Ventilation, and Air Conditioning Systems, Components, and How They Work

Your home’s heating, ventilation and air conditioning (HVAC) system might be one of its largest components, but unless something goes wrong you probably give very little thought to it. However, understanding how a HVAC systems work helps homeowners troubleshoot potential problems and become a more informed homeowner.

Heating

The heating aspect of your home’s HVAC system is carried out by your furnace. Depending on the style of heat distribution in your home, you may either have electric baseboards, a gas forced air furnace, or radiant heat system (also known as a boiler) installed. For our purposes, we’ll focus on gas-powered forced air systems, as they are the most popular system installed in homes today.

All central heating systems consist of a burner, heat exchanger, blower, and a flue. The burner is what engages when the thermostat calls for heat, and it delivers the fuel to your heat exchanger to begin the heating process. The heat exchanger intakes air and turns the fuel and air mixture into heat that will ultimately be sent through your home’s ductwork. The heated air is then transferred to the air distribution system. The blower is part of this distribution system, and is what ultimately moves the heated air through your ductwork and into the various rooms of your home. We’ll discuss the flue in the next section, as it’s a significant part of the ventilation aspect of the HVAC system.

A boiler-based or hydronic heating system works in a similar manner as a gas-powered forced air system, heating water within the boiler for distribution via piping to radiators located in the various rooms of a house, which then give off heat. Electric baseboards or registers contain a heating element that heats up when the thermostat calls for heat. Some have a blower to help distribute the heat, but some simply give off radiant heating.

Ventilation

The ventilation aspect of your home’s HVAC system is comprised of the flue and vent pipes. It might also involve a fresh air intake pipe or vent. The fresh air intake helps to bring the heated air to the correct temperature before it is distributed throughout the house. The flue and vent pipe are responsible for keeping the air in your home safe to breathe. It works by exhausting harmful byproducts of the combustion process, such as carbon monoxide and other noxious fumes, outside the building. The flue will open and close accordingly in order to ensure there is no backup of dangerous exhaust into your home.

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Dıffeent Types Of Hvac Systems

Dıffeent Types Of Hvac Systems

For most people, heating and cooling will account for as much as half of the energy they use. With this in mind, it’s important to choose a HVAC system that will meet your comfort needs, without drawing on excess power and escalating your cost of living.
• People living in hot or cold climates might go for a single stage system, designed to produce just heating or cooling. These tend to be inexpensive, but are also rather inefficient and will typically be working at capacity even when it’s not required.
• More advanced models will offer variable fan speeds to cut down on power use, however they remain inefficient when compared to multi-stage systems, and are thus more expensive to run over the long term.
• Zoned systems, on the other hand, have been designed to heat or cool individual parts of your home. This is done by designing zone valves and dampers inside the vents and ductwork that selectively block the flow of air. For people with larger properties this is of immeasurable value as it prevents the system from heating or cooling areas in the home that are not in use.
• HVAC systems can also be built to offer humidity control, and both humidifiers and dehumidifiers can be added as options to heating and cooling systems. People that live in very dry environments or the tropics find these additions to the system essential. With that being said, some people prefer to install separate humidifier or dehumidifier systems, so that they can manage the humidity of their environment without also having to turn on the air conditioner.

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How Aır Curtaıns Reduce Coolıng Costs

How Aır Curtaıns Reduce Coolıng Costs

Nearly all business owners are wary of costs and search for effective ways to save money. In warmer months, most businesses turn their thermostats down and make use of air conditioning systems. Maintaining an optimum temperature is essential for ensuring that customers enter the building- and that they wish to stay there.

However, controlling the climate of premises can be a costly affair. Air curtains can reduce cooling costs by preventing the amount of warm air that enters through an entryway. They will also prevent the loss of cooled air, by blocking the entry of hot air when a door is opened and closed. Both of these features mean that you can maintain a desired temperature, without needing to use air conditioning as often, or for as lengthy periods of time. This reduces the amount of energy used by air conditioning units, therefore saving your business valuable money spent on cooling costs. Air curtains also prevent outside contaminants- such as dust and insects – from entering an establishment. This can be invaluable for customers or employees with sensitivity to these contaminants, and can be particularly useful in months where hay fever is prominent.

Air curtains come in a variety models. Most are designed to fit above eight foot doorways; however, many companies have created models to fit in smaller or larger gaps. Air curtain length can also vary- some need only to be a little shorter than the width of the doorway, whereas other companies find that extra-long curtains, or several in a row, have a greater impact. You also choose the right strength to fit the requirements of your company. For example, air curtains made for walk-in freezers must work harder to account for the drastic difference in temperatures. Businesses that work in dusty or bug infested areas may look for air curtains that are best at filtering such contaminants.

Whatever your needs, air curtains are certain to save you money on the costs of climate control, and may even bring you a greater return as customers are happy to stay on site longer.

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How air conditioning condensers work?

How air conditioning condensers work?

The air conditioner condenser is the system component that removes heat from the system. The condenser is a heat-exchange surface that permits the transfer of heat from the system refrigerant to the air outside. The heat comes from the space that is being cooled and from the heat generated during the compression process. The air outside for residential systems, must be at a lower temperature than the refrigerant to allow heat transfer to occur. This rejection of heat causes the hot vapor refrigerant coming from the compressor to condense. The purpose of the condenser is to condense the refrigerant to a liquid. The temperature at which the refrigerant will condense is called the condenser saturation temperature.

The Condensing Process

The refrigerant leaving the compressor is superheated and well above the saturation temperature, so it must first be cooled before it can condense. The process of removing the superheat from the discharge refrigerant is referred to as desuperheating. The desuperheating process removes superheat and is a sensible heat exchange since it can be measured with a thermometer. Although the temperature is changing, the pressure will remain the same. The purpose of the first process is to reduce the refrigerant to the condenser saturation temperature.

Once the refrigerants temperature drops to its condenser saturation temperature then it will begin to change state. The second process of the condenser is to change the refrigerant from a vapor to a liquid. The refrigerant goes under a latent heat transfer which cannot be measured, when changing from a vapor to a liquid. Since the refrigerant is still warmer then outside it will still continue to give away heat as a liquid. The condenser has condensed the refrigerant.

Subcooling is the third process of the condenser it cools the refrigerant to a temperature below the condenser saturation temperature. One degree of subcooling is one degree below the condenser saturation temperature. Ideal subcooling temperature is about 20 degrees below the saturation temperature. Subcooling gives the system a high-pressure high-temperature liquid to enter the metering device.

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Types of Gas Burners

Types of Gas Burners
Types of residential gas burners include atmospheric injection, yellow (luminous) flame, and power burner units. Their classification is determined by the firing method used. Gas burners can also be divided into two broad classifications based on whether they are specifically designed as integral parts of gas-fired heating equipment, are used to convert a furnace or boiler from one fuel to another. The latter are called conversion burners and, at least outwardly, resemble the gun-type burners used in oil- fired appliances. Gas conversion burners are commonly designed and manufactured with integral controls so that they can be installed as a unit in the existing furnace or boiler.
Note
The burner(s) producing the heat in a gas-fired appliance is some- times called the main gas burner. Do not confuse the main gas burner with the pilot gas burner. The function of the latter (where it is used) is to light the gas flowing to the main gas burner.

Gas burners may also be classified as inshot and upshot types, depending on the design of the burner tube. The burner tube of an inshot gas burner is commonly a straight, adjustable venturi that extends horizontally from the unit. An upshot gas burner is characterized by a burner tube that extends horizontally from the unit and then bends to assume a vertical position.

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Function of Condenser

Function of Condenser

In a cooling cycle of a refrigeration system, heat is absorbed by the vapor refrigerant in the evaporator followed by the compression of the refrigerant by the compressor. The high pressure and high temperature state of the vapor refrigerant is then converted to liquid at the cond. It is designed to condense effectively the compressed refrigerant vapor.

There are basically three types of condensing unit depending on how the heat is removed by the condensing medium which is usually water, air or a combination of both.

• Air-Cooled types are usually used in the residential and small offices applications. They are used in small capacity systems below 20 tons. The advantages of using this design include not having to do water piping, not necessary to have water disposal system, saving in water costs and not much scaling problems caused by the mineral content of the water. It is also easier to install and has lower initial cost. There isn't much maintenance problems. The disadvantages are that it requires higher power per ton of refrigeration, has shorter compressor life and on days when most cooling is required, the least is available. 

• The circulation of air-cooled type can be by natural convection or by forced convection (usually using blower or fan). Due to its limited capacity, natural convection is used in smaller applications such as freezers and refrigerators. In forced convection, air is circulated by using a fan or blower that pulls the atmospheric air through the finned coils. Internally, the refrigerant circulates through the coil and air flows across the outside of the tubes.

• Water-Cooled There are 3 types commonly being used. They are shell and tube, shell and coil, and double tube. The most commonly used is the shell and tube type and are usually available from two tons up to couple of hundred tons. This design has lower power requirements per ton of refrigeration and the compressors can last longer compared to the air-cooled type. A water cooling tower is frequently used for higher capacity application.

• Evaporative type which is a combination of water and air-cooled.

Air-Cooled and Water-Cooled Comparison Summary

• Air-cooled type operates at higher head pressure or condensing pressure, hence reducing the capacity of the compressor and increases the power intake. In general, a 2 hp water-cooled system will require the same refrigeration as a 3 hp air-cooled system.
• The maintenance costs of water-cooled type is about three to four times the air-cooled type. Air-cooled type maintenance is usually limited to regular lubrication of fan and motor bearings. Water-cooled type requires cleaning from algae and bacteria. Scales on the tubes are removed by using acid compound. Proper water treatment is also critical to the operation of the cond.

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Expansion Valves

Expansion Valves

Expansion valves are devices used to control the refrigerant flow in a refrigeration system. They help to facilitate the change of higher pressure of liquid refrigerant in the condensing unit to lower pressure gas refrigerant in the evaporator.

The term "low side" is used to indicate the part of the system that operates under low pressure, in this case the evaporator. The "high side" is used to indicate the part of the system that operates under high pressure, in this case the condenser.

Types of Expansion Valves

There are basically four types of valves that are in used. These valves are also refer to as metering devices.

• Automatic Exp. Valves
• Thermostatic Exp. Valves
• Capillary Tubes
• Float Valves

Automatic Expansion Valve regulates the flow of refrigerant from the liquid line to the evaporator by using a pressure-actuated diaphragm. It maintains a constant pressure in the evaporator.

The setback is that it is not efficient if the load fluctuates hence this type is not suitable for use in air conditioning as the load fluctuates a lot during its operation.

Thermostatic Expansion Valve uses a valve mechanism to control the flow of liquid refrigerant into the evaporator coil. The flow is controlled by the pressure in the evaporator.

This type of metering device is able to operate well when the load fluctuates and hence is suitable for use in air conditioning system. When the evaporator warms, the valve provides a higher flow rate amd when it cools, it reduces the flow rate.

It is also commonly refer to as TXV, TEV or TX valve. There is a sensing bulb which detects the temperature of the coil and is usually located at a higher temperature within the evaporator.

The bulb must be clamped firmly to the coil to ensure proper sensing. When the temperature of the evaporator increases due to the demand for cooling, the pressure in the bulb will also increase hence pushing the spring to open the valve.

Similarly, when the temperature of the evaporator reduces due to a lack of demand for cooling, the pressure in the bulb will drop hence causing the spring to close the valve.

Capillary Tube is a tube with small internal diameter and could be coiled for part of its length. It is installed to the suction line. A filter-drier is sometimes fitted before the tube to remove dirt or moisture from the refrigerant.

This device is simple, does not have any moving part and lasts longer. In order to use this device, the amount of refrigerant in the system must be properly calibrated at factory level.

Due to its lower cost compared to TXV, this metering device is used in units that are produced in large quantity such as room or window air conditioners.

Depending on the capacity design of the system, the capillary tube internal diameter that is commonly used range from 0.031" to 0.065" and the outer diameter from 0.083" to 0.130".

Float Valve is actuated by a float that is immersed in the liquid refrigerant. Both low-side float and high side-float are used to control the flow of liquid refrigerant.

The low-side float helps to maintain a constant level of liquid refrigerant in the evaporator. It opens when there is no liquid in the evap. and closes when there is liquid in the evap.

The high-side float is located at the high pressure side of the system and maintain a constant level of refrigerant in the condenser. When the compressor operates, the condensed refrigerant flows to the float chamber and opens the valve.

This causes the refrigerant to flow into the evaporator where it is stored. As the liquid level falls in the float chamber, the valve opening will close hence preventing the liquid from flowing to the evap.

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Evoporator

Evoporator
The evaporator works the opposite of the condenser, here refrigerant liquid is converted to gas, absorbing heat from the air in the compartment.
When the liquid refrigerant reaches the evaporator its pressure has been reduced, dissipating its heat content and making it much cooler than the fan air flowing around it. This causes the refrigerant to absorb heat from the warm air and reach its low boiling point rapidly. The refrigerant then vaporizes, absorbing the maximum amount of heat.
This heat is then carried by the refrigerant from the evaporator as a low-pressure gas through a hose or line to the low side of the compressor, where the whole refrigeration cycle is repeated.
The evaporator removes heat from the area that is to be cooled. The desired temperature of cooling of the area will determine if refrigeration or air con¬ditioning is desired. For example, food preservation generally requires low refrigeration temperatures, ranging from 40°F (4°C) to below 0°F (-18°C).
A higher temperature is required for human comfort. A larger area is cooled, which requires that large volumes of air be passed through the evaporator coil for heat exchange. A blower becomes a necessary part of the evaporator in the air conditioning system. The blower fans must not only draw heat-laden air into the evaporator, but must also force this air over the evaporator fins and coils where it surrenders its heat to the refrigerant and then forces the cooled air out of the evaporator into the space being cooled.

Fan Speeds
Fan speed is essential to the evaporation process in the system. Heat exchange, as we explained under condenser operation, depends upon a temperature differential of the air and the refrigerant. The greater the differential, the greater the amount of heat exchanged between the air and the refrigerant. A high heat load, as is generally encountered when the system is turned on, will allow rapid heat transfer between the air and the cooler refrigerant.
A blower fan turned on to its highest speed will deliver the most air across the fins and coils for rapid evaporation.
For the coldest air temperature from the evaporator, operate the blower fan at the lowest speed so the heat will be absorbed by the refrigerant from the air
Problems of Flooded or Starved Evaporator Coils
Changing the state of the refrigerant in the evaporator coils is as important as the air flow over the coils. Liquid refrigerant supplied to the coils by the expansion valve expands to a vapor as it absorbs heat from the air. Some liquid refrigerant must be supplied throughout the total length of the evaporator coils for full capacity.
A starved evaporator coil is a condition in which not enough refrigerant has been supplied through the total coil length. Therefore, expansion of the refrigerant has not occurred through the whole coil length, resulting in poor coil operation and too-low heat exchange.
A flooded evaporator is the opposite of the starved coil. Too much refrigerant is passed through the evaporator coils, resulting in unexpanded liquid passing onto the suction line and into the compressor.

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HVAC FAN TYPES

HVAC FAN TYPES 
All types of fans are designed for the sole purpose of delivering air. In an HVAC unit, most furnaces contain one or more fans, and different fans are used for different applications. There are three basic fan types that are usually encountered in the HVAC industry. The Axial Fan, the Forward Curved Centrifugal Fan and lastly, the Backward Inclined Fan.

Axial Fan
Axial fans, also known as propeller fans, are engineered to move a low volume of air under low static conditions (static pressure is the resistance to air flow). These types of fans are low cost, and don’t work well when it faces resistance. Since propeller fans are low cost, most are built to run on Single Phase Voltages. These types of fans are more suited for applications with lower air volumes and pressures.

Axial fans can usually be found positioned on top of an HVAC Rooftop or home compressor that is outside a house. A basic HVAC system which doesn’t run a heat pump is designed with condenser coils which remove heat from an area. These coils have fins that need air to move through them so as to remove heat. Since these sections don’t require a high power fan, an axial fan is the best and most cost efficient solution.

Centrifugal Fan

Centrifugal fans look similar to hamster exercise wheels. These types of fans produce more pressure for a given air volume than axial fans. They are usually noisier as compared to axial fans and are suited for applications with higher air flow volumes and pressures. It has 3 types of drive mechanism: direct, belt, or variable drive. Inside the HVAC Rooftop system, you will find a centrifugal fan. These fans should be strong enough to overcome all the resistance of the room’s duct-work. This is where axial fans are inadequate. Centrifugal fans move a large quantity of air while overcoming all the resistance or static pressure of the duct-work so that it can provide adequate air flow throughout the facility.

Backward Inclined Fans

These types of fans are designed to handle large volumes of clean air as needed in heating, ventilating, and air conditioning systems. These are also used in many industrial air supply and exhaust applications. There are some HVAC Rooftop units and HVAC accessories that may contain one or a series of backward inclined fans.

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Different Types of Fans Used in the HVAC Industry

Different Types of Fans Used in the HVAC Industry

In the Middle East, commercial and industrial units are steadily growing and the demand for HVAC products in the area is remains high. To be able to supply the needs of different industries, many HVAC companies make sure that they deliver high quality products, and one of the most important HVAC products are the different types of fans used. In HVAC equipment, there are different types of fans that are used.

 HVAC FAN TYPES 
All types of fans are designed for the sole purpose of delivering air. In an HVAC unit, most furnaces contain one or more fans, and different fans are used for different applications. There are three basic fan types that are usually encountered in the HVAC industry. The Axial Fan, the Forward Curved Centrifugal Fan and lastly, the Backward Inclined Fan.

Axial Fan
Axial fans, also known as propeller fans, are engineered to move a low volume of air under low static conditions (static pressure is the resistance to air flow). These types of fans are low cost, and don’t work well when it faces resistance. Since propeller fans are low cost, most are built to run on Single Phase Voltages. These types of fans are more suited for applications with lower air volumes and pressures.

Axial fans can usually be found positioned on top of an HVAC Rooftop or home compressor that is outside a house. A basic HVAC system which doesn’t run a heat pump is designed with condenser coils which remove heat from an area. These coils have fins that need air to move through them so as to remove heat. Since these sections don’t require a high power fan, an axial fan is the best and most cost efficient solution.

Centrifugal Fan
Centrifugal fans look similar to hamster exercise wheels. These types of fans produce more pressure for a given air volume than axial fans. They are usually noisier as compared to axial fans and are suited for applications with higher air flow volumes and pressures. It has 3 types of drive mechanism: direct, belt, or variable drive. Inside the HVAC Rooftop system, you will find a centrifugal fan. These fans should be strong enough to overcome all the resistance of the room’s duct-work. This is where axial fans are inadequate. Centrifugal fans move a large quantity of air while overcoming all the resistance or static pressure of the duct-work so that it can provide adequate air flow throughout the facility.

Backward Inclined Fans
These types of fans are designed to handle large volumes of clean air as needed in heating, ventilating, and air conditioning systems. These are also used in many industrial air supply and exhaust applications. There are some HVAC Rooftop units and HVAC accessories that may contain one or a series of backward inclined fans.

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Copper Tubes

Copper Tubes

Copper tube is one of the components that is needed in air conditioning and refrigerant system. The tube is used as a path for the refrigerant to flow between system components and to contain it from escaping to the atmosphere. Sizing, installation layout and fittings must be done properly to ensure that the system runs efficiently.

During installation, it is of utmost importance that moisture, dirt and other contaminants are prevented from entering the system. These foreign particles will affect the performance of the system and may even cause damage to some of the components.

During the production of the copper tube, the inside of the tube has been cleaned and dried before being sealed at both ends to ensure that it remains that way. You must check to make sure that the refrigerant that is going to be used does not react with the copper. Ammonia refrigerant will react with copper hence it should not be used. Instead, the stainless steel tubing type will have to be used.

Types Of Tubing

There are basically two types of tube namely the hard-drawn and the soft type.

Hard-Drawn Copper

This type of tubing is rigid, hard and stiff. It is not easily bent and should not be bent. Fittings are used to obtain the configuration needed for the installation. The length commonly available is 10 feet or 20 feet. There are three standard weight with different wall thickness for each type. Type K has the thickest wall tubing followed by Type L and Type M. If you need a higher pressure tube, thicker type is to be used to ensure it can handle the pressure of the refrigerant. Type L outer diameters typically starts from 3/8 inch followed by 1/2 inch, 5/8 inch, 3/4 inch, 7/8 inch, 11⁄8 inch, 13⁄8 inch, 15⁄8 inch, 21⁄8 inch and 25⁄8 inch.

Soft Copper 

The soft copper is flexible and comes in rolls of 25 feet or 50 feet. The typical outer diameter ranges from 1/8 inch to 13⁄8 inch. Markings of ACR are done on the tubing to indicate that it is used for air conditioning and refrigeration purposes. During production, these parts are cleaned and dehydrated to remove the moisture from the tube. It is then filled with nitrogen gas before being capped.

Insulation & Pre-caution 

In order to prevent the refrigerant from absorbing unnecessary heat from the ambient, the copper tube is insulated between the evaporator and the compressor at the low pressure side of the system. Hence you will be able to see the insulation material being wrapped around the copper tubes for this purpose. It is also to prevent condensation from happening on the tubes.

When cutting the tubing to the required length, make sure that you use a proper tool such as the tube cutter.The burr on the inside of the tube that resulted from the cutting must be removed from the tube as these contaminants will affect the flow of refrigerant as well as affecting the performance of the system.

When bending is required, take note that only the soft copper type can be bent. Use a proper tube bending springs to prevent flatten or kink.

When soldering or brazing is required, make sure that you have being trained to do this and adhere strictly to the instructions of the manufacturers.

Wear eye protection when particles are being released in the air as a result of your action.

When you are doing annealing process where you heat up the tube and allow it to cool slowly, make sure that you use a flared flame over a distance of 1 feet at a time and not concentrating the heat on one location.

Ensure the work place is well ventilated especially when fumes is being emitted as a result of your work. Do not breathe in excessive gas and adhesive.

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Chilled-water and Cooling-tower AC Units

Chilled-water and Cooling-tower AC Units
Although standard air conditioners are very popular, they can use a lot of energy and generate quite a bit of heat. For large installations like office buildings, air handling and conditioning is sometimes managed a little differently.
Some systems use water as part of the cooling process. The two most well-known are chilled water systems and cooling tower air conditioners.
• Chilled water systems - In a chilled-water system, the entire air conditioner is installed on the roof or behind the building. It cools water to between 40 and 45 degrees Fahrenheit (4.4 and 7.2 degrees Celsius). The chilled water is then piped throughout the building and connected to air handlers. This can be a versatile system where the water pipes work like the evaporator coils in a standard air conditioner. If it's well-insulated, there's no practical distance limitation to the length of a chilled-water pipe.
• Cooling tower technology - In all of the air conditioning systems we've described so far, air is used to dissipate heat from the compressor coils. In some large systems, a cooling tower is used instead. The tower creates a stream of cold water that runs through a heat exchanger, cooling the hot condenser coils. The tower blows air through a stream of water causing some of it to evaporate, and the evaporation cools the water stream. One of the disadvantages of this type of system is that water has to be added regularly to make up for liquid lost through evaporation. The actual amount of cooling that an air conditioning system gets from a cooling tower depends on the relative humidity of the air and the barometric pressure.
Because of rising electrical costs and environmental concerns, some other air cooling methods are being explored, too. One is off-peak or ice-cooling technology. An off-peak cooling system uses ice frozen during the evening hours to chill interior air during the hottest part of the day. Although the system does use energy, the largest energy drain is when community demand for power is at its lowest. Energy is less expensive during off-peak hours, and the lowered consumption during peak times eases the demand on the power grid.

Another option is geo-thermal heating. It varies, but at around 6 feet (1.8 meters) underground, the earth's temperature ranges from 45 to 75 degrees Fahrenheit (7.2 to 23.8 degrees Celsius). The basic idea behind geo-thermal cooling is to use this constant temperature as a heat or cold source instead of using electricity to generate heat or cold. The most common type of geo-thermal unit for the home is a closed-loop system. Polyethylene pipes filled with a liquid mixture are buried underground. During the winter, the fluid collects heat from the earth and carries it through the system and into the building. During the summer, the system reverses itself to cool the building by pulling heat through the pipes to deposit it underground
For real energy efficiency, solar powered air conditioners are also making their debut. There may still be some kinks to work out, but around 5 percent of all electricity consumed in the U.S. is used to power air conditioning of one type or another, so there's a big market for energy-friendly air conditioning options

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Basic Types of Check Valves

Basic Types of Check Valves

It is very important for HVAC mechanical engineer to know about various valves being used in mechanical industry.Various check valve types have been developed to cater to the diversified requirements in piping systems in various applications.These various types of check valves offer many advantages and disadvantages .One type of check valve ideal for one applicationmay be misfit for another application.Plant engineers have to look into many factors to decide which type of valve would be they using in that particular application.

Following are the main check valve types used in various applications.

1. Swing Check Valve
2. Tilting Disk Check Valves
3. Lift Check Valves
4. Piston Check Valves
5. Butterfly Check Valves
6. Stop Check Valves
7. Other Check valve types (Ball check valve, diaphragm check valve etc)

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+90 212 343 50 40

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