The chilled water system for a 27-story building has a pump located at ground level. The lost head in a vertical riser from the pump to an equipment room on the twenty-seventhfloor is 40ftof water, and the pump produces 270ft of head. What is the pressure on the suction side of the pump for a pressure of 8 psig to exist in the riser on the twenty-fifth floor

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The chilled water system for a 27-story building has a pump located at ground level. The lost head in a vertical riser from the pump to an equipment room on the twenty-seventh floor is 40ft of water, and the pump produces 270ft of head. What is the pressure on the suction side of the pump for a pressure of 8 psig to exist in the riser on the twenty-fifth floor

Assume 12ft of elevation per floor

48.68 psig

Explanation:

First  we calculate the elevation of the building

hb = 27 story * 12ft per floor/story

hb =  324 ft

given that the head lost in the vertical riser hL = 40 ft

now the delivery head required in the riser on he 27th floor;

hd = 8 psig *  (2.31 ft / 1 psig)

hd = 18.46 ft

Now calculate the suction head required by balancing the energy per unit weight of water, considering pump as the control volume

hp = (hb + hL + hd) - hs

hs = hb + hL + hd - hp

where hp is the head developed by the pump (270 ft)

hb is the elevation of the 27th floor of the building ( 324 ft)

hL is the head lost in the vertical riser ( 40 ft)

hd is the head required to exist in the riser on the 27th floor (18.46 ft)

so we substitute

hs = 324 ft + 40 ft + 18.46 ft - 270 ft

hs = 112.46

so 112.46ft * (1 psig / 2.31 ft)

= 48.68 psig

the order for strong to weak forces such as

strong nuclear force → electromegnetic force → weak nuclear force → gravitational force

the fundamental forces are those forces that act between to objects or element to make interactions. there are four types of fundamental forces such as strong and weak nuclear forces (due to protons and electrons), electromagnetic force (due to the motion of electrons) and gravitational force (due to orbital movement of the planet). if these forces are arranged on the basis of their maximum strength then the order is

strong nuclear force → electromegnetic force → weak nuclear force → gravitational force

electromagnetic shielding is the practice of reducing the electromagnetic field in a space by blocking the field with barriers made of conductive or magnetic materials. shielding is typically applied to enclosures to isolate electrical devices from their surroundings, and to cables to isolate wires from the environment through which the cable runs. electromagnetic shielding that blocks radio frequency electromagnetic radiation is also known as rf shielding.

the shielding can reduce the coupling of radio waves, electromagnetic fields and electrostatic fields. a conductive enclosure used to block electrostatic fields is also known as a faraday cage. the amount of reduction depends very much upon the material used, its thickness, the size of the shielded volume and the frequency of the fields of interest and the size, shape and orientation of apertures in a shield to an incident electromagnetic

from wikipedia