Question

A two-pipe direct return chilled water system with an expansion tank is used to circulate water for cooling three identical loads in a commercial building. Each load is connected with a balancing valve, zone valve and thermostat. Given that the cooling capacity of each load is 50 kW, density of water 1000kg/m3, a specific heat of water Cpw 4.185 kJ/kg K and gravitational constant 10 m/s2. (a) Sketch a schematic of the system illustrating all the components. (6%) Legend Expansion tank Balancing valve Thermostat Circulator (pump) 2 Chiller www Load Zone valve (b) Determine the water circulation mass flow rate in kg/s, and volume flow rate in L/s, required by the chiller if the water temperature difference between inlet and outlet of each load is 6°C (796) (c)If the head loss in the system is 18.3m, and the pump is 80% efficient, calculate the pump power input. (6%) (d) Give a disadvantage of this system. Suggest one modification to improve and illustrate with a schematic. (6%)

Answer 1

gatves Volumeれ00mk2- looo 13.2

ooc 2