Help required

[Charltonkerry]

I am an industrial refrigeration designer, who is looking to design a very energy efficient industrial refrigeration system (If you are interested 1000kW of cooling with a room temperature of 1°C) to keep energy consumption to a minimum I have decided to use an evaporative condenser (Condenses hot high pressure gas into a relatively low temperature but still high pressure liquid refrigerant) by a combination of air and water being sprayed over a series of tubes.

Whilst I know the maximum wet bulb temperatures for certain cities within the UK, I would like to find the following info:

1. When do the high wet bulb temperatures occur i.e. is it a hot summers afternoon just before a storm or could it be a muggy winters night. From a personnel point of view info such as when and why the wet bulb varies would be interesting i.e. in summer is it possible to have low wet bulb temperature and if so how and why?

2. Is there somewhere (I tried the met office & typing in wet bulb in google search) i can see a graph of a typical year of wet bulb temperature for an area of the UK, i.e I am trying to find out how much it varies and would like to know the maximum, minimum and the mean for a town in the UK. All this is information is readily available for dry bulb temperature.

3. If somebody has a simple explaination of wet bulb temperature that could be understood by non technical people this would also help me.

Thanking you in advance for any assistance anyone can offer, also apologising in advanced if i have posted this in the wrong topic.

Regards

Kerry

[Terminal Moraine]

The wet bulb temperature is basically a measure of evaporative cooling and varies according to the relative humidity of the air.

A wet bulb temperature at or very close to the dry bulb temperature, at any time of year, is indicative of saturated or nearly saturated air and a large difference between wet and dry bulb temperature indicates dry air.

Very dry air in summer can result in very low wet bulb temperatures relative to the dry bulb temp; for instance a dry bulb temp' of 30c with a relative humidity of 20% ( very low for this country ) would give a wet bulb temp' of 17c.

As warm air is capable of holding much more moisture than cold air the same % relative humidity at a high dry bulb temp' will require a much larger depression of the wet bulb than the same relative humidity in cold air.

For instance at 30c quoted above the wet bulb needs to be 13c lower to give a relative humidity of 20% but if the dry bulb were only 5c it would require a wet bulb depression of only about 5.5c to achieve the same humidity.

I don't have any information on the average wet bulb temp' for different months of the year at any given location but it would be possible to calculate it if you could find a map/chart of relative humidity and you knew the average dry bulb temperature for a given time of day.

At my own location in January for instance, the relative humidity is around 90% and the mean temp' is 2.4c, this would give a mean wet bulb temp of 1.7c. The equivalent stat's for the afternoon in July would be mean humidity around 70%, mean temp' about 18.5c and therefore a mean wet bulb of 15.4c.

I'm not sure how much use this information is to you but it's about the best I can do.

T.M

[Charltonkerry]

TM thank you very much for the info, I must admit I started off thinking that finding historical wet bulb data was going to be easy, how wrong can you be, even finding accurate electrical measuring equipment has proved to be a major project, mind you this has now been sourced. I have just designed a very basic system which has been installed in a food production factory in the derby area and the results are being assussed. Initial findings indicate the power savings of 20% are acheviable with a payback of under 3 years. When the power input of the combined motors are over a 1000kW/hour at design conditions then this is worth saving. No doubt we will be fine tuning this and even more power will be saved. I will investigate if our basic equipment can start recording the wet bulb temperature as this would at least give us easy to access to historical data.

With the installation being fined tuned our client has asked us how many tonnes of carbon he is saving, again we have been scouring the internet but cannot find how to convert kw into tonnes of carbon. Been on the goverment web site but they only deal with households (i.e. turning off a light bulb), has anybody got any idea for links for industrial users?

Sorry to be a pain,

Regards

Kerry

PS am i putting these sort of questions in the correct area's or shouldn't i even be asking these sorts of questions on this website, wouldn't like to upset anyone as obviously info is being used for both enviromental and commerical.

[johnholmes]

try the Met O site although when you start to question them via their e mail address they will charge you?

http://www.metoffice.gov.uk/index.html