Dear Friends can anybody tell me w

[nabeel3]

Dear Friends
can anybody tell me what is "Mean coincident wet bulb temperature " (MCWB) means. I am working in a project in which the HVAC specifications says that for HVAC SYSTEMS 5 Tons and larger in addition to calculating load by means of Summer design Dry bulb and MCWB the cooling load shall also be calculated at summer design wet bulb temperature and Mean coincident dry bulb temperature. I need to understand what MCDB and MCWB temperature means...Thank u in advance..

 

[lukaiENG]

It means the mean (aka average) wet bulb temperature coincident with (at the same time as) the peak dry bulb temperature.
In other words, on your hottest hour on you summer design day, the MCWB temperature is the expected wet bulb temperature you will expect to experience at that time.
This is important as it allows you to establish the enthalpy of the outdoor air condition and accurately size your cooling coils.

Similarly, there are tables for peak wet bulb temperature with MCDB. these tables are used for sizing evaporative components i.e. cooling towers or dehumidification.

I suggest you plot the various points on a psychrometric chart and this will help you visualize the relationship of the different options.

Note, the ASHRAE tables also include extreme wet bulb and dry bulb temperatures which you may want to consider for some applications where control of temperature is critical (clean rooms, data centers etc)

 

[nabeel3]

Thanks lukaiENG for the answer....