Air conditioner sizing

No heat source sounds implausible. What conditions is the ship operating in? Air conditioning is probably unneccessary at latitudes exceeding 55degrees. How well is the room insulated?

A very small one!

In general you use 1 ton of cooling for every 400 square feet of space. Do all of the calculations you want but this is pretty accurate and it usally comes pretty close to the complex solution. You have 130 square feet. Therefore you would likely use 1/2 tons of cooling.

Yup! The people give off heat, the structure passes heat form the accommodation underneath, from the sun outside, from the electrics etc inside. In fact as with all calc's in this area you need to calc your heat load max - min in all latitudes, hottest to coldest. Then you need to know the number of air changes you want? Is there a toilet or smokers? Come-on give us some more details.

Hi Hesham,

You could try using the u value figures from the Ashrae design manual for the structure that you are dealing with, plus add for ventilation and body load. Usually something like the following. bare glass U val. is 6.5watts per m2 * TD . Be aware though that the Ashrae figures are worked on something like an outside air speed of 5 ms. I would imagine that on board a vessel at sea you would have to allow somewhat more than that.

regards

Coben

OOPs, try SQM * 6.5 * TD

From the pshychrometric chart enthalpy scale

ventilation will be something like Kj per Kg dry at start less Kj per Kg dry at finish giving KJ to remove * weight of dry air * volume of air being moved by the fan/s, converted from Kj to Watts. This will include room volume plus ventilation.

regards

Coben

sizing an air conditioning system requires calculations of heat loads. this process is complex to a non-HVAC engineer. however, there are certain nominal figures they use. depends on your location around the world these vary from place to place and from time to time. take the maximum load for sizing less diversity factor. your 12 sq. m. area would probably need 1 Ton of Refrigeration (3.517 kW) considering that radiation and conducted load would be the greatest loads. internal load would come from occupancy and fresh air loads. the above size is equivalent to 3.4 m²/kW (ave.) similar to a public area.

My experience in ships in the tropics is to use the biggest unit you can afford. With all the windows on the bridge, no insulation, the electronics operating 24 hrs a day and the crew entering and exiting all the time you are going to need all the cooling you can get.

Mike

I'd say somewhere around 3 to 5 tons. You will be in the tropics a lot and there is a lot of solar heat gain with all the glass, and probably little or no insulation, so you'd need more capacity on account of that.

i beg to disagree that 5tons would be appropriate. this is not a freezer or cooler room! 2.4 sq. meter per TR? you must be kidding! take your calculator: at 400 cfm per tr nominal air flow with ambient at 95 deg F, what's you load? Q=m*cp*delta T. my question is (i am not a sailor) does the heat while on sea even in the tropics reach 95 deg. F? I have been in the desert of Saudi Arabia, where ambient dB would be as high as 115 deg. F, i could not justify a 5 TR air conditoner for 12 sq. meter of floor area.

On a bridge of this size, we use a 1 ton air conditioner. Typically there is little to no insulation in the top or sides. The large glass areas make the job even tougher. Remember you will need to also take into account what percentage of the time the outside door will be open. In reality, it takes a whole lot more than you would typically plan for.