Heating Ventilation Air Conditioning

  • Clean Room Solutions

    Clean Room Solutions

    Our Cleanroom Solutions designs, manufactures and supplies customized modular components for the construction and installation of these controlled environments. Leading specialist supplier of modular controlled environment solutions for use in the pharmacare, micro-electrical and data storage sectors.

  • Ventilation and Humidity Control

    Ventilation and Humidity Control

    In cool climates, natural ventilation (opening windows) or mechanical ventilation (fans, exhaust systems) to control excessive moisture and humidity . In warmer climates, the heating, ventilation, and air conditioning (HVAC) system can pull warmer, humid air inside. In this case, the ventilation system may help create indoor humidity problems unless the system also dehumidifies the air.

  • Comfort Cooling

    Comfort Cooling

    The need for comfort cooling arises, therefore, when requirements in respect of the thermal climate also include requirements in respect of maximum permissible indoor temperatures. HVAC (Heating, Ventilation and Air-Conditioning) systems used in order actively to cool buildings

COMFORT COOLING

The use of comfort cooling is growing rapidly in India. Most landlords of commercial premises are very aware of the importance of being able to provide good indoor climate conditions for existing and new tenants. At the same time, occupants are becoming increasingly aware of the requirements that can be posed in respect of the indoor environment.  The indoor environment consists of many parameters. However, the one that an occupant of an office building notices immediately is the thermal climate. It has
long been accepted that the indoor temperature must not be too low: increasingly, there is pressure that it should not be too high, either.

Various types of comfort cooling system are being installed, both in new building projects and in connection with conversion or renovation.  The prime requirement in respect of the indoor climate in a building is that room temperature should be at a comfortable level, regardless of the weather conditions outside. In addition, the indoor air must be acceptably clean, lighting and acoustic conditions must be good etc. Nevertheless, the first and foremost condition for a building to be usable at all is that the indoor temperature is acceptable.

As soon as the ambient temperature is lower than the indoor temperature, heat flows out from the building through its boundary surfaces (the building envelope). At the same time, the building also loses heat through air infiltration, i.e. the inward leakage of outdoor air into the building through gaps and cavities in walls, roofs, doors and windows. Bearing in mind the fact that the indoor temperature in most buildings is maintained at a little  over 20 °C, this means, throughout most of the year, the building is losing heat to its surroundings. When buildings are used, there is almost always internal generation of heat, through the use of various appliances and equipment, from lighting and from the occupants themselves. There is also a heat input from insulation, which contributes to the internal heat generation.

Internal heat generation in residential buildings is normally relatively modest.  In everyday language, the surplus heat that has to be removed from buildings in order to maintain the indoor temperature below some previously determined maximum permissible temperature is referred to as the cooling requirement. In other words, the cooling requirement of the building is exactly the same as its heat surplus.

The climate control system in a building has to maintain both the thermal climate and the air quality. Maintaining the thermal climate consists primarily of keeping the temperature of the indoor air within given limits. Maintaining the air quality consists of controlling the ‘cleanliness’ of the indoor air by supplying a sufficient quantity of outdoor air to ventilate the interior of the building. Maintenance of air quality sometimes also includes ensuring that given concentrations of particles and/or gases are not exceeded.


The need for comfort cooling arises, therefore, when requirements in respect of the thermal climate also include requirements in respect of maximum permissible indoor temperatures. In general, HVAC (Heating, Ventilation and Air-Conditioning) systems used in order actively to cool buildings can be divided up into three main types:
_ all-air cooling systems
_ all-water cooling systems
_ combined systems
(With cooling supplied both by air and by water)


All-air cooling systems: The design air flow rate in these systems, and thus the necessary sizes of ventilation ducts, is determined by the design cooling requirement. In other words, it is the thermal requirements, and not the air quality requirements, that determine the necessary air flow rate. In existing buildings, it is normally both difficult and expensive to replace the ventilation duct system. If the existing ducts cannot transport sufficiently large air quantities to meet the cooling requirements, all-water cooling systems will usually be installed in connection with conversion or modernization.

The cooling system must be able to deal with variations in the cooling requirement, whether over the day or over the year. The two basic types of all-air cooling systems are the constant air flow system and the variable air flow system, although there are also combinations of the two methods.

Constant air volume systems (CAV systems): In such systems, the temperature of the air supplied to the building can vary, but the air flow rate is kept constant. Such systems are referred to as Constant Air Volume (CAV) systems.

Variable air volume systems (VAV systems) The air flow rate to each room is varied as necessary, but with maintenance of a constant supply temperature, i.e. the supply temperature does not change even if the load changes. However, the supply air temperature is normally changed in step with the time of year, as a function of the ambient temperature. Systems of this type are referred to as Variable Air Volume (VAV) systems.

All-water cooling systems: Systems of this type supply all-water cooling to the individual rooms, with the ventilation system designed purely to maintain the air quality.  Systems of this type are often chosen in connection with conversion or renovation projects. There is usually space above the false ceilings to install the water pipes needed for distribution of cold water throughout the building.

Combined systems All-air and all-water cooling systems can be combined in many ways. One such need for a combined system is if all-air cooling is used, but the cooling requirement is so great that an all-air cooling system alone is not capable of dealing with it satisfactorily, as such high air flow rates would be required that draughts would be unavoidable It is also possible to combine all-air cooling systems so that certain parts of the building, or certain rooms, are cooled by a VAV system, while other parts of the building are cooled by a CAV system.

Cooling supply devices:

Chilled beams These are units which, by natural convection from a finned heat exchanger, cool the air in the room. They may also be combined with the supply air terminal device in order to provide both functions and, in many cases, to increase the cooling capacity of the baffle. Some chilled beams can also incorporate a heating function.

Cooling panels : Cooling panels can be hung from the ceiling, Cold water flows through an aluminium plate, which transfers heat from the air to the cold water. The panel cools the warm room air and also cools the room surfaces by low-temperature radiation. These panels are produced in a number of versions, e.g. for mounting flat against the ceiling, hanging, or for integration in a false ceiling. Most of their cooling capacity is provided by radiation.

Fan coil units: These are units by which both heating and cooling can be supplied to a room (although not at the same time). A fan coil unit incorporates a fan which circulates the room air through the unit, in which the air is either heated or cooled as required. The two heat exchangers (heating and cooling) are supplied with hot or cold water from a central unit in the building. This type of room cooler unit can meet the highest cooling requirements, but it also has the highest noise level.

Induction units: These are units by which both heating and cooling can be supplied to a room (although not at the same time). When in use, the ventilation air for the room is supplied through the induction unit. It flows through a nozzle with high velocity, which therefore has the effect of inducing air from the room through the heating or cooling heat exchangers. This makes it possible to heat or cool the room in a single unit, without the use of a fan.

Cooling supply devices: Cooling can be supplied to a room in a number of different ways. The following are brief descriptions of how chilled beams, cooling panels, fan coil units and induction units operate. Fan coil units and induction units are normally positioned below windows in the outside walls.

Chilled beams
These are units which, by natural convection from a finned heat exchanger, cool the air in the room. They may also be combined with the supply air terminal device in order to provide both functions and, in many cases, to increase the cooling capacity of the baffle. Some chilled beams can also incorporate a heating function.

Cooling panels
Cooling panels can be hung from the ceiling. Cold water flows through an aluminium plate, which transfers heat from the air to the cold water. The panel cools the warm room air and also cools the room surfaces by low-temperature radiation. These panels are produced in a number of versions, e.g. for mounting flat against the ceiling, hanging, or for integration in a false ceiling. Most of their cooling capacity is provided by radiation.

Fan coil units
These are units by which both heating and cooling can be supplied to a room (although not at the same time). A fan coil unit incorporates a fan which circulates the room air through the unit, in which the air is either heated or cooled as required. The two heat exchangers (heating and cooling) are supplied with hot or cold water from a central unit in the building. This type of room cooler unit can meet the highest cooling requirements, but it also has the highest noise level.

Induction units:
These are units by which both heating and cooling can be supplied to a room (although not at the same time). When in use, the ventilation air for the room is supplied through the induction unit. It flows through a nozzle with high velocity, which therefore has the effect of inducing air from the room through the heating or cooling heat exchangers. This makes it possible to heat or cool the room in a single unit, without the use of a fan.

Free cooling It is a common misconception that it is always necessary to run some form of mechanical chiller as soon as cooling is required. This is not actually the case: instead, it is often possible to use the outdoor air to provide what is known as free cooling. There is no generally accepted definition of what free cooling is.  However, a common interpretation is that it refers to the ability to supply cooling when it is required, without having to pay for the actual generation of the low temperature.

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