Heaters over open shop doorways

[Tyre Smoke]

I am posting this here, because I know someone sciency will know the answer. I should point out I got a 'U' in my physics 'O' level, so please keep it a simple as possible please!

Why do shops, like Next, Dotty P's, etc put blow heaters facing downwards or horizontally over the wide open doorways of their shops?

I always thought heat rises, so heating the air at the top of the shop space is not going to help is it? Also, isn't there a huge amount of heat wasted by bleed to the outside colder air?

Tell me it's a logical thing to put a mahoosive blown air heater over an open doorway - and why, please! It's driven me mad since I was little.

[Stu R]

Behavioural rather than science related for the large part - it's for the same reason they put AC over them in the summer (in some places). It provides an instant 'ahh' to a significant percentage of the footfall upon entry, and highlights the miserable weather outside when you leave. If your first and last experience of the store is an almost instant, increased comfort level (or leaving decreases your comfort level) you typically stay longer, spend more, and are more inclined to return.

Also, if they went upwards, it'd be altogether more entertaining for the chaps, miserable for women in skirts, and it wouldn't form a barrier, it'd be dispersed.

Edited by Stu R on Friday 9th November 14:05

[GWC]

They are called air curtains and are designed to create a barrier between inside and out keeping the cost of heating the building down.

[Tyre Smoke]

GWC said:

They are called air curtains and are designed to create a barrier between inside and out keeping the cost of heating the building down.

How?

Stu, see what you are saying, but it's surely a ruinously expensive way of keeping your shoppers inside?

[GWC]

http://www.thermoscreens.com/en/air-curtain.html

[Stu R]

Tyre Smoke said:

GWC said:

They are called air curtains and are designed to create a barrier between inside and out keeping the cost of heating the building down.

How?

Stu, see what you are saying, but it's surely a ruinously expensive way of keeping your shoppers inside?

That's not their main purpose, as said it's a barrier from the elements. Retail stores consume a ton of energy, another 10-15kw on for all that benefit isn't much really.

[mrmr96]

Stu R said:

Tyre Smoke said:

GWC said:

They are called air curtains and are designed to create a barrier between inside and out keeping the cost of heating the building down.

How?

Stu, see what you are saying, but it's surely a ruinously expensive way of keeping your shoppers inside?

That's not their main purpose, as said it's a barrier from the elements. Retail stores consume a ton of energy, another 10-15kw on for all that benefit isn't much really.

Surely the air stream from the roof hits the floor and then will "splash" with half going outside, and the other half going inside? So any warm air on the inside of the air stream will tend to be returned inside. And likewise cold air on the outside will be driven down by the stream, but then "splash" back outside once the stream hits the floor?

[Munter]

mrmr96 said:

Stu R said:

That's not their main purpose, as said it's a barrier from the elements. Retail stores consume a ton of energy, another 10-15kw on for all that benefit isn't much really.

Surely the air stream from the roof hits the floor and then will "splash" with half going outside, and the other half going inside? So any warm air on the inside of the air stream will tend to be returned inside. And likewise cold air on the outside will be driven down by the stream, but then "splash" back outside once the stream hits the floor?

Just to confirm. You are both saying the same thing yes?

[Odie]

The reason they blow down is coz generally women dont like everyone to see their knickers.

[mrmr96]

Munter said:

mrmr96 said:

Stu R said:

That's not their main purpose, as said it's a barrier from the elements. Retail stores consume a ton of energy, another 10-15kw on for all that benefit isn't much really.

Surely the air stream from the roof hits the floor and then will "splash" with half going outside, and the other half going inside? So any warm air on the inside of the air stream will tend to be returned inside. And likewise cold air on the outside will be driven down by the stream, but then "splash" back outside once the stream hits the floor?

Just to confirm. You are both saying the same thing yes?

I think so. I was trying to work out how they achieve the aim of lowering heating costs. I think they do it by making a "wall" to keep the hot air inside. There will be some wasteage as the jets are heated, but the technique would also be somewhat effective with unheated air. (Albeit that would feel unpleasant as you passed through, but it would keep the shop toasty.)

[Morningside]

Dear shop,
[claim] I am starting to thin on top and they are starting to burn. [/claim]

[Simpo Two]

I think it's the same principle as my cunning plan to heat only the cavity in the walls of a house. With the cavity maintained at a certain temperature, the interior cannot drop below it... yes you lose heat through the wall, but the volume of air to heat is a tiny fraction of the house.

[mrmr96]

Simpo Two said:

I think it's the same principle as my cunning plan to heat only the cavity in the walls of a house. With the cavity maintained at a certain temperature, the interior cannot drop below it... yes you lose heat through the wall, but the volume of air to heat is a tiny fraction of the house.

Not sure if serious?

[The Nur]

mrmr96 said:

Not sure if serious?

I think the clue was in the "cunning plan" part

[mrmr96]

The Nur said:

mrmr96 said:

Not sure if serious?

I think the clue was in the "cunning plan" part

...I seeee. :-/

[The Nur]

mrmr96 said:

...I seeee. :-/

At least I hope it was.

Merely my own interpretation.

[Tyre Smoke]

Okay, so I understand what it does, but surely there must be a more effective way of heating a shop?

Meanwhile the cunning cavity wall heating..........

[Ultuous]

Tyre Smoke said:

surely there must be a more effective way of heating a shop?

Yes, shut the 'king door! But, as already suggested, it's considered the best way of 'trapping' the heat inside whilst satisfying people psychologically, despite the inefficiency!

[Simpo Two]

mrmr96 said:

Not sure if serious?

If I was any good at physics I might see whether it's cheaper to keep X volume of air at (say) 19C with a faster heat loss than 1000X volume at 19C with a slower heat loss. If you have a box surrounded by a constant 'jacket' at 19C, the interior of the box cannot cool down.



They all laughed when Edison invented sound you know...

[Munter]

Tyre Smoke said:

Okay, so I understand what it does, but surely there must be a more effective way of heating a shop?

It's not to heat the shop as such. It's to stop the heat escaping. So keeping the door shut is more effective...not great for trade though. Revolving doors also work.