How can we calculate the maximum pump pressure for chilled water system for a 20 story building
maximum stress tanks have a bladder interior them.The air is extra to the bladder to create a cushion of air, because of the fact the stress interior the tank builds up. Rule of thumb; while the pump is off and the stress interior the device is enable all the way down to 0, there ought to be 2# below shrink-in stress on your stress swap. i.e.- in the adventure that your stress swap is a 20/40, meaning it cuts in at 20# of stress and cuts out at 40# of stress, you may choose 18# on the bladder. in case you have an previous sort tank devoid of bladder, it ought to have an air quantity administration that provides air each time the pump comes on. Any air you upload to this sort of tank will ultimately get away so which you may choose to repair the situation with the air quantity administration. that's complicated and you may incredibly choose a provider individual to try this. e mail me and that i'll enable you recognize the thank you to do it if certainly you have an previous sort, bladderless, tank. desire to help!
Once a closed circulating system is filled, the circulating pump needs only to deliver the pressure difference need to take care of circulation losses due to friction and to flow controls. The friction losses will be through the chiller tubes plus through the cooling coils plus thru the longest total circulation piping run. Add to this the pressure drop through the most restrictive regulating valve in the system. This cannot be determined without knowledge of the piping sizes , the components and the respective flows. To take a guess, I would say you would be looking at a circulating pressure rise through the pump of around 30 psi. The static pressure from elevation , about 0.44 pounds per ft of height will be the same in both the supply and return risers and at both the suction and and discharge connections of the pump. So the height of the building need not be considered in the circulaton pressure losses. However the pressure rating of components will need to be suitable for that static pressure. Usually pump casings and pipe fittings are rated for cold water pressures adequate to the approximate static pressure of 90-100 psig on that ground floor or even in the basement of a 200 ft high building. where the pump is assumed to be located.
In addition to what was said earlier you will also need to consider the following. Pipe frictional losses will need to be calculated. If there is a control valve or flow element then need to add 3 to 5 psi. If the chilled water goes thru a piece of equipment there will be a pressure loss across that, (example - cooling coil on an air handling unit, air separator etc) this can range from 3 to 20 psi, the equip vendor should be able to provide this. If your pumps are on the ground floor, you might be able to neglect the pressure due to elevation if the loop remains pressurized by the pump(s). Might be a good idea to have an engineer review this who has sized pumps before.
20 storey's, let's say 200 feet. 200 x 0.433 = 86.6 psi. at ground level and about 0psi at the top. The pump, in order to deliver water to the top would need a pressure in excess of 87 psi but, the volume of pumped water would need to be high enough to cope with a number of people using it at the same time as this will starve the upper storeys if insufficient. Generally, a tall building will have booster pump stations on other floors up the building to ensure adequate supply.
the question is not stated in such a way that a response is merited. What, exactly, is the problem? Minimum pressure might be enough to push a water column 20 stories... max pressure? how about 726 or a million psi?
