Description
See attached pdf for assignment
Unformatted Attachment Preview
ME 390
SummerHomework
2012 – Take Home
Mid Term #3
ME 390
#16540
Assignment
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 12϶F 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 12϶F condenser water temperature drop at full capacity.
ASSIGNMENT:
1 Chilled water system:
1. What
is thewater
total Chilled
Water System
GPM demand
full design
capacity?
Draw
a chilled
piping schematic
showing
adequateatelbows,
tees,
control valves, coils,
2. Assuming
a maximum
ft/s flow
velocity
main
chilled water piping,
chiller
(evaporator),
chilled10
water
pump.
Show in
allthe
pipe
lengths.
A) what will the main pipe diameter be?
Determine the required flow rate.
B) if this pipe is galvanized steel pipe, what will the per foot friction loss
Size the chilled water supply and return piping so it is operates at full flow capacity at the
(in units of feet head per foot length) in the main piping at full flow?
smallest pipe size such that it will be laminar or transitional flow (i.e. next standard size
3. Assuming
a 20% in
increase
of “equivalent
length” to the piping system from
smaller
would result
turbulent
flow).
elbows & fittings, and assume an equal friction design approach, what is the
Determine the maximum pressure drop of the system. Plot the system curve.
systems 1) total equivalent length? & 2) total head loss at full design flow?
Determine
the attach
chilledawater
pumpofperformance
requirements.
Select
a properly
4. Draw and
schematic
the Chilled Water
system piping
showing
pipe sized chilled
water pump from an online pump manufacturer, and plot the pump curve with the system
sizes and section lengths.
curve.
2 Condenser water / Cooling tower system:
Draw a condenser water piping schematic showing adequate elbows, pipe lengths, chiller (condenser),
5. What is the total Condenser Water System BTU/hr demand at full design capacity?
condenser water pump, and the cooling tower. Show all pipe lengths.
6. What is the total Condenser Water System GPM demand at full design capacity?
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 ȴT (϶F)
(this applies to sensible heat transfer only, not
applicable to the latent portion in the Cooling Tower).
Purchase answer to see full
attachment
