Cooling load of X-ray machine

[lzh007]

For a general radiography suit in a hospital, how do we guess the cooling load of the X-ray machine. The input is 150 KVA, output 80 kW, What's the percentage is appropriate for calculation?
On the ASHRAE handbook, the table shows average load corresponding to nameplate load. It does not make any sense to me. For example nameplate 1725 w, average 480 w, nameplate 2070 w, average 18 w.
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[gerhardl]

Suggestion (without any particular knowledge to X-ray machines) for rough estimate (maybe this is obvious?):

a) First, assuming that cooling have to be sufficient to cool during a continous, long-lasting periode of 100% use (worst case).

b) Check with supplier: Does a '100%' use also imply that power consumption is 100% all the time, or is there a lower ground-laod with peaks for exposure? Supplier to advice on maximum allowed or possible for both.

c) From a and b to make an 'avarage' worst case for power intake/time.

d) With result from c, check for possible dimensionon for cooling equipment if whole load to be cooled. This estimate again to be reduced by natural heat leakage to environment.

Other factors may also reduce size and extent of cooling:
- natural 'resting periodes of equipment'
- cooling already provided for in arrangement/placing of components from supplier (natural cooling)
- allowed heating up of elements, could be far above surrounding temperature.
- strict or 'none strict' environment control in room
- room size and already present room climatic control or natural circulation.
- supplier info! (Is any extra cooling actually needed, or is influence to environment not more than percentage of total possible load, reducing the load to be not more than
the effect of some extra people in the room)

 

[briand2]

I did a similar at a hospital job here in the UK a few years ago; I'm afraid I don't have the data to hand at the moment.

The manufacturer's information for the machine (it was a Simulator, a sort-of X-ray machine used for cancer treatment) showed not only maximum power input but also typical "duty cycle", etc. As I recall, in normal use, it would be on for no more than 12 minutes each hour, over about six sessions. This therefore reduced the air conditioning load.

There was one complication; it could also be used in a "test" mode, for the hospital's "physicists", which would entail full load being applied for a longer time (up to 30 minutes, I seem to recall). However, as there were not patients in the room during this period, it was OK to let the room temperature rise a bit!

Hope this helps; best advice is to get similar information about the machine with which you are involved.

Brian

 

[IRstuff]

You need to determine the duty cycle of the machine. How long is it on and how often? Since the room temperature behaves as if it were low-pass filtered, knowledge of the average power is mandatory to determine the correct heat load.

TTFN

FAQ731-376

 

[TADiep]

I recommend talking with the manufacturer. As ASHRAE states, "heat gains from medical equipment is very specific and varies greatly from application to application."



----
A green thought..."We don't inherit the earth from our ancestors, we borrow it from our children." (unknown)

 

[marcoh]

As TADiep suggested contact the manufacturer. It's a highly specialised bit of equipment and 'estimates'could very well back-fire on you in the future.

If all fails log the power consumption on a similar machine and see how much power it actually consumes?