Answer the following six questions

Floor standing unit heaters are an ideal method of heat transfer in a large factory or warehouse, as they can generate heat by direct firing very quickly.

A 2000 M3 are of space could be heated to its design temperature in about 10 minutes.

Floor standing heaters take very little maintenance, only a service once a year, and as the unit is floor standing it is readily accessible and easy to work at if a problem did occur.

As the installation of a unit heater tends to be in a factory installation, the unit heater can tend to get damaged by forklifts and moving machinery which have and adverse effect on the life expectancy of a unit heater.

Floor standing unit heaters especially direct fired units are very noisy and tend not to be used in any other installations apart from factories and warehouses which is a great limitation on the plant.

Unit heaters are a very permanent job if you decide to change the layout of the factor and you want to move the unit heater it is a big job so in that resect

Indirect air heaters are used for space heating and have the advantage of being simple in both construction and operation. Air is passed over the heat exchanger by a fan or fans and is subsequently heated to about 30oC to 40oC. The warm air is supplied into a space through outlet diffusers, which can direct the air where it is required and throw heated air up to about 10 meters from the point of discharge.

These units are suitable for large areas, which require heating since large amounts of heated air can be supplied. Warehouses, factories, workshops and supermarkets use this type of heating and outputs range from 10kW to 100kW

Warm air heaters can be easily concealed into a wall. Therefore leaving all wall spaces free.

Warm air heaters have very good control and can maintain a constant room temperature possibly better than any of its rivals. Warm air heaters react quickly to a change room temperature conditions by diverting the flow of water from the coil to the return in the pipework; this in turn will stop any heat coming from the fan convector and provides maximum control.

Warm air heaters are very effective when heating a large area as they produce forced hot air into a room. It distributes the air quickly and effectively and is ideally used in a sportshall application where by the fan convectors can be concealed within a wall and still produces force air to heat the space required.

At present Warm air heaters are widely used even at low temperatures and have some advantages over radiators.

Warm air heaters operate by heating air, which passes over the finned pipe through which warm/hot water passes. The fins are mechanically fixed to the tube(s) and extend the heating surface so that all the heat output is purely convective. The heating tubes are enclosed in a cabinet with louvres at the bottom to allow cooler air to enter and louvres at the top to emit heated air into the space.

Warm air heaters may also have some form of control such as a damper to alter the flow of air. Natural convectors rely on air movement over the heating element by natural convection and forced Warm air heaters use a fan or fans to assist the movement of air.

Warm air heaters tends to be noisy in their general running and therefor wouldn’t be suited to office or libraries.

Warm air heaters requires a lot of maintenance regards cleaning of filters and cleaning of motors. As fan convectors draw in the air it can also draw in dust to the filter and motor which causes long term problems.

Warm air heaters are not as cost effective as a radiator for example. The fan convector is usually some 500% dearer to buy than a radiator and as a fan convector uses electricity to run the fan motor dearer to run as well.

Fabricated radiant heated ceiling panels using medium temperature hot water can provide a surface temperature between 100 – 180 ^oc , which produces a powerful radiation output.

The product is one of the most cost effective and energy efficient radiant heaters available with a pleasing appearance. Its method of construction allows ease of fixing in a wide range of applications. In addition, the heating grid and face panels are installed separately as first and second fix items respectively. This means that the colored and contoured face panelwork is not subject to site damage during early stages of construction.

It is usual to suspend these panels vertically along walls, or between columns in a large workshop, at a height of 3 to 4 meters’ above floor level. They may also be fixed horizontally or be inclined at an angle at high level close to the roof or ceiling.

Radiant panels require controls in order that the panels operate effectively and efficiently. These controls (Diverting Valves) require a lot of maintenance on the actuators. This can be a big disadvantage for examples in a factory, as your controls for each panel may be 10 or 15 m up at roof level where the panels are and to carry out a regular maintenance check is a major job.

Embedded radiant panels can be very useful in a medical situation where by no forceful air movement is permitted i.e. operating theatre. Embedded radiant panels would be a very useful and workable method of heat transfer in this type of situation.

Embedded radiant panels do not inhibit or take up any wall space, which can be a great advantage in the following situations

Sports halls, hospital wards, corridors, classrooms, laboratories, factories, open plan office areas and workshops

These consist of either a vitreous enameled metal plate or a ceramic tile behind which a resistance element is mounted within a casing.

Panels of this type operate at a temperature of about 250oC and have ratings in the range 750 W to 2 kW; they are normally used in washrooms in industrial situations.

Fabricated radiant panels as shown below are particularly suited to large factory spaces when supplied with high or medium temperature hot water or steam. These systems can provide surface temperatures in the range of 100-150oC and the flat metal plates produce a powerful radiation output, which may be felt at some distance.

The panels consist of a 15-mm sinuous pipe coil welded to a heavy gauge mild steel front plate. The rear of the panel may be treated as follows: {a} exposed coil, {b} double sided, {c} insulated back, and {d} shielded back. An alternative form of exposed coil is to weld the plate in the centre of the pipes.

HTHW Radiant panels in a hospital situation

Radiant panels using MTHW can run at very high surface temperatures (100 – 150 ^co).

This can be very dangerous in a school application because it pupils can get access and touch the panel it will cause serious burning to the skin or if the waterways within the panel leak in a class room the can again cause serious burning.

If a radiant heated ceiling panel is used in a factory situation and installed at lower levels than the roof this can inhibit the maximum working height for the machinery within the factory.

In an engineering application where by cranes are used this will cause all sorts of problems.

Radiators do not strictly speaking 'radiate' all their heat into the space but up to 80% may be convected, typically for a double panel radiator about 30% of total heat output is radiated and 70% is emitted by convection.

Radiators can be described by various means but the type of material used in the manufacture is the main method of distinction. The four radiator types as listed below show various methods of manufacture and style to suit different conditions.

{a} The simple convoluted panel types which may be single, double or more - Steel.

{b} The column type - Cast Iron.

{c} A sinuous coil panel type which is similar to a radiant panel - Steel.