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To all Sorry the bldg is approx 29 yrs old. Added info: The spec calls for the 40 Ton AC unit to be either Trane or Carrier. Vendors have replied only with price. We don't know the mfgr. With wrong Design CFM and evaporatr air flow dp, how will performance be effected? Thanks Sailoday

We are replacing a roof top Air Conditioner. The 12 story high rise bldg is 35 yrs old and was designed to have pressurized corridors/hallways. Presently, due to age, etc, the bldg is not pressurized. The engr wrote a spec for the replacement AC. He use desig conditions of inlet air to...

Compositepro and mint julep With flow in =flow out,won't the expansion valve open further to Carry the heat load? If so, how does this lower pressure in the evaporator? Thanks so far for your prompt replies.

Can someone provide the theoretical and practical reasons that low refrigerant will cause icing on the outside of the evaporator? Thanks

Whether flow or non flow, delta h is the integral of vdp. With flow, change of kinetic energy should also be considered for the isentropic process under consideration Regards

Whether

For the non flow process described, dU=-pdv or dh=vdp Regards

Berkshire With the outside compressor at ground level and the split system evaporator below the ground level lobby and a small section of vertical return from evap, does that rule out a commercial 2 speed compressor?

Berkshire The compressor is located about 150 feet from the bldg. The remaining split part of the system is below the lobby from where a few ducts deliver the cooled air.

We are replacing a split AC system (25 yrs old) for the lobby of our condominium bldg. Capacity is approx. 7.5 tons. I asked the hired engineer to consider a 2 speed AC motor or 2 stage compressor in his specification so that we could then evaluate the higher initial cost vs long term savings...

For those inclined to do a some applied math. Used product solution for a disc and superposition. Result will be in terms of Bessel and Fourier series. This will give a closed form solution for temp at any point (for example, center) vs. time. Regards Sailoday 28

Piping diam does matter if Kinetic Energy is to be accounted for. If change in velocity is small, then KE can be neglected. Energy input is w*change in stagnation enthalpy. Regards

317069 (Mechanical) Cost of labor,etc for removal. If piping can be used then it is a substantial cost savings when doing the replacement.

Please note, the main unit (compressor, condenser, evaporator, etc) is to be replaced. The question is --what concerns are there with regard using existing buried piping (150 ft)when the refrigerant is replaced (say R410 vs R22). With regard to flow resistance, I would think the expansion valve...

Presently the lobby of our building is cooled by a 10 ton Air Conditioner --- the compressor and condenser are located about 150 ft from the bldg. An inside air handling unit with and evaporator is located in the bldg. Air conditioner compressor, evaporator, etc are about 30 yrs old and are to...

FredRosse(Mech) A closed form solution of upstream mass vs time is obtainable under the following assumptions/conditions. Source tank--adiabatic Perfect gas with constant specific heats. Connecting piping is adiabatic and frictionless. Flow is choked. Regards Sailoday28