Design of heat supply systems for ventilation and calorifers

One of the most important systems which serve for normal operation of the forced air ventilation is the heating supply for ventilation and calorifers. The main function is air heating which is taken from outside in winter time before it is served indoors.

Calorifers or air heaters are divided into the following types:

• Hot water calorifers
• Steam radiators
• Glycol heaters
• Gas-fired air heater
• Electric calorifer

A standard heating supply system for ventilation (except for electrical heat systems) consists of the following:

• A mixing shunt to adjust the coolant flow through the calorifer and is implemented by means of partial opening of three- or two-way valves
• Stop valves which allow the manifold assembly to be maintained
• The pipe-routing from the heat source to calorifer

Hot water calorifers are one of the widely used air heaters. Engineering of the heat supply system for ventilators is possible if the customer can provide placing mixing shunts either in the engineered or already built premise. More often such system are used in trade or entertainment centers, sporting complexes of large areas due to their economical efficiency. Water heated up to 90/70°C or 80/60°C is used as a heat transfer agent. It should be noted that the water from the heating system may not be used for heating supply of hot water calorifers.

Overheated steam with the temperature of 110/70°C is used as a heat transfer agent in steam radiators. Power efficiency of such agent is higher, however it is necessary to use ventilation equipment with heat exchangers which are aimed for the use of steam. Moreover, pipe-lines mounting and insulation assembly shall be executed more carefully. More often steam radiators are used in ventilation facilities of large industrial areas.

In case air supply units are placed outside the building or in the premises without heating, then it is possible to use glycol heaters. Here the ethylene glycol solution in water with the volume of 10% - 40% serves as a heat transfer agent. This type of the heat transfer agent prevents calorifers e from freezing in winter time. When using glycol radiators the mixing shunt shall be combined with transitional heat exchangers and an additional pumping group. The disadvantage of the heating supply system is the partial heat loss (5-10%) at the level of the transitional heat exchanger. At the process of engineering the use of gas-fired air heaters should also be considered. Natural gases - methane or liquefied petroleum (hydrocarbon) gases are used as heating medium. One may also come to use liquefied natural gas. Input ventilation air is heated in the recuperative air heater by means of the heat which is generated in the course of gas burning in the combustion chamber. It is recommended to use gas-fired air heaters at the production areas which are located at a distance from the heating main or boiler plant.

Electric calorifers are also referred to air heaters. They are often used in ventilation units in case there are no other ways to implement another type of heating supply, for example, by the reconstruction of buildings. They may also be mounted on the pipe mains closely to the entrance into the premise. The solution depends on the possibility of connection to the power line.

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