Retain heat, retain efficiency

Adopting a holistic approach to heating in factories could pay rich dividends. Andrew Saxon looks at how the use of air curtains alongside space heaters can strike an efficient balance

Many factory and warehouse managers will have been tasked with reducing their operational energy usage. The first thing that people may consider when addressing this issue, and where arguably the biggest improvements can often be made, is the building’s heating system.

Large commercial and industrial buildings are notoriously difficult to heat due to their open layouts, high ceilings and loading bay areas that let out vast amounts of heat each time the doors are opened. Traditional solutions include ceiling-mounted radiant or warm air heaters. However, they are not always the most efficient solution, particularly when only certain parts of the warehouse are occupied.

To overcome the difficulties associated with traditional methods of heating large commercial and industrial buildings, more innovative technologies have been developed.

However, adopting the latest innovations in heating technology is really only one half of the problem solved. To maximise investment in heating equipment, businesses must ensure that the heat generated stays within the building. This can be done through measures such as improving roof and wall insulation, and by installing air curtains above loading bay doors.

In most factories and warehouses the loading bay area is a bustling hub of activity, with vehicles constantly going in and out. However, each time loading bay doors are opened, an incredible amount of heat can be lost into the atmosphere. Air curtains effectively minimise the amount of cold air coming into a building through a doorway, while keeping the warm air inside.

Without an air curtain, heat will escape through an open door as natural convection causes it to be lost at the top, and replaced at the bottom by cold air coming in. Air curtains work by disrupting and minimising this flow, providing a continuous stream of air circulated across a doorway serving a conditioned space.

Some people might think that by installing an air curtain, they are simply adding to a building’s carbon footprint by running an additional piece of equipment. In fact, the energy saved by an air curtain far outweighs what it uses.

If we take, for example, a 4m high and 3m wide doorway and simulate the heat that is lost when the door is opened (based on an outside temperature of 0oC and a temperature of 20oC to be maintained inside); 79kW of warm air is lost to the atmosphere, and the incoming cold draught requires 43kW to bring it up to room temperature. This means that when the door is opened without an air curtain, a total of 122kW of heat is needed to maintain the 20oC temperature inside. However, when an air curtain is installed with an output of 52kW, comfort is maintained inside the building, saving 70kW.

So, an air curtain can be a very economical and efficient solution. By correctly installing one above a loading bay door, over 80 per cent of the building’s energy can be retained inside, resulting in huge savings on energy bills and a big reduction in the company’s carbon footprint.

In addition to reducing heat loss, air curtains can also be used to improve the effectiveness of extraction/filtration systems in factories and processing plants where odour, smoke, gas or dust particles need to be contained to avoid causing a nuisance to neighbouring properties and the general public.

It’s often assumed that if polluted air is being extracted and filtered, only fresh air will enter when the doors are opened. However, contrary to this belief, as a result of natural convection the warmer (polluted) air within the building will still escape to the outside.

By creating an invisible barrier between the clean and the polluted area, ambient air curtains, installed in each delivery doorway, can draw in the air that is about to escape from the building. The polluted air will be blown down towards the floor and, before touching it, will return back into the building.

The installation principles are different to standard air curtains – for example much lower discharge velocities are required – but Biddle can provide advice and guidance.

As businesses strive to lessen their impact on the environment, it is important to take a 360o view to ensure that the heat generated is retained within a building. By considering the issue of heat loss, building owners can be certain that the steps they are taking to improve the efficiency of their heating systems will not result in money simply disappearing out of the door. And, as a further benefit, air curtains can improve the effectiveness of extraction/filtration systems, helping to prevent odour, smoke, gas or dust from escaping.


Andrew Saxon is marketing manager at Biddle Air Systems


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