Fluid mechanics

Step by step solution needed 

 

The building shown below has three occupied floors and a mechanical basement, each are 15 feet high. Each floor is air conditioned with it’s own air handler. The 1st floor air handler unit (AHU) has a chilled water cooling coil with a 50 Ton cooling capacity, the 2nd floor AHU has a 65 Ton cooling coil, and the 3rd floor AHU has an 85 Ton cooling coil. Each coil has a 9 ft. pressure drop at full design flow. Each AHU coil chilled water control valve is designed to have a 12 ft pressure drop at full design flow.

The 200 Ton chiller in the basement has a 7 ft pressure drop across the evaporator when at full design flow. The chiller and all of the AHU coils are designed for a 120F delta T across the evaporator / coils when at full design capacity. The chiller is a semi-hermetic closed drive centrifugal operating at 70% efficiency, the frictional and motor efficiency losses are rejected thermally through the condenser water system. The condenser on the chiller at full capacity has a 15 ft pressure drop.

The cooling tower on the roof has a condenser water inlet at the top in an open (air) hot basin. The top of the cooling tower is 15 ft above the roof. The cold basin that has the condenser water return piping connection at the bottom of the tower is 4 ft above the roof. The tower is designed to achieve a 120F condenser water temperature drop at full capacity.

ASSIGNMENT:

1 Chilled water system:

Draw a chilled water piping schematic showing adequate elbows, tees, control valves, coils, chiller (evaporator), chilled water pump. Show all pipe lengths.

Determine the required flow rate.

Size the chilled water supply and return piping such that when operating at 4% of full flow capacity the smallest standard pipe size possible will produce laminar or transitional flow (i.e. next standard size smaller would result in turbulent flow), use .000017 ft2/s for kinematic viscosity.

Determine the maximum pressure drop of the system. Plot the system curve.

Determine the chilled water pump performance requirements. Select a properly sized chilled water pump from an online pump manufacturer, and plot the pump curve with the system curve.

2 Condenser water / Cooling tower system:

Draw a condenser water piping schematic showing adequate elbows, pipe lengths, chiller (condenser), condenser water pump, and the cooling tower. Show all pipe lengths.

Determine the required flow rate.
Determine the condenser water return pipe size (flow back to the tower) assuming it has 10% friction

loss (hL).

With this total return (pump discharge) flow and head capacities, and using the same size piping on the condenser water supply line (from roof to chiller), determine the condenser water pumps total head and GPM requirements, as well as the NPSHA. Select a properly sized condenser water pump from an online pump manufacturer to meet these conditions.

_____________________________________________________________________________________

Show all work, including formulas used, assumptions made, schematics, equipment selection submittals, charts and graphs, etc..

1 Ton of air conditioning = 12,000 BTU/hr
For water flow BTU/hr = GPM x 500 x ΔT (0F)