Handbook of air conditioning and refrigeration / Shan K

31.24 CHAPTER THIRTY-ONE
Storage cooling capacity
Maximum refrigeration load
Charge process duration
Discharge process duration
Inlet temperature during charging T i
Limiting outlet temperature during
discharging T o
Inlet temperature during discharging T re,i
Maximum volume flow rate
Tank diameter
Tank height
Tank volume
Usable tank volume
There are two 1200-ton (4220-kW) and two 900-ton (3164-kW) centrifugal chillers to serve zone 1
and zone 2, as shown in Fig. 31.10. There are also five chiller pumps, one of which is a standby.
Two variable-speed building pumps are installed for each zone, one of which is a standby pump.
Three storage pumps are used for chilled water storage, one of which is standby.
Concentric Double-Octagon Diffusers
Concentric double-octagon diffusers are used at both the top and bottom of the stratified tank, as
shown in Fig. 31.7a. Each octagon introduces 50 percent of the total volume flow during the charging
process. Over time, a double-octagon arrangement provides nearly twice the effective linear
length for diffusers of a single-octagon arrangement.
The total effective length of the eight diffusers in the outer octagon is 559 ft (170 m). For a total
flow of 0.5 � 5120 � 2560 gpm (162 L/s) through the outer octagon, the volume flow rate per linear
ft (0.30 m) of diffuser is
V˙ dif
l dif
The kinematic viscosity of water at 42°F is 1.66 � 10 � 5 ft 2 /s, so the inlet Reynolds number is calculated
as
Re i � V˙ dif
l dif� w
Similarly, the inlet Reynolds number for inner octagon is 1068. Both are close to the upper limit of 805.
The acceleration of gravity g � 32.2 ft/s 2 , and
� i � � a
� i
For a common inlet opening height h i � 5.64 in, or 0.47 ft (0.14 m), the inlet Froude number for
diffusers in the outer octagon is calculated as
Fr i �
�
�
2560 � 0.1337
559 � 60
�
0.0102
� 615
�5 1.66 � 10
62.4263 � 62.3864
62.3864
24,500 ton� h (861,420 kWh)
3200 tons (11,251 kW)
16 h
8 h
40°F (4.4°C)
42°F (5.6°C)
56°F (13.3°C)
5120 gpm (323 L/s)
105.5 ft (32.2 m)
41 ft (12.5 m)
2.68 million gal (10,144 m 3 )
90%
� 0.0102 ft 2 /s
� 0.00064
0.0102
[(32.2)(0.47) 3 � 0.22
0.5 (0.00064)]