Consider a chiller plant that has to provide a cooling capacity of 800 TR. Water-cooled chiller...

Consider a chiller plant that has to provide a cooling capacity of 800 TR. Water-cooled chiller with a cooling tower is adopted. However due to the availability of waste heat, two different chillers are studied: R-123 centrifugal chiller and LiBr absorption chiller. Some of the design parameters are already fixed: - Evaporating temperature at 5 ºC - Condensing temperature at 42 ºC - Chilled water temperature at 7 ºC and 12 ºC respectively - Condensing water temperature at 32 ºC and 38 ºC respectively for the centrifugal chiller - Outdoor design condition at 33.5 ºC DB and 28 ºC WB Assume that the waste heat for the absorption chiller can heat up the generator to 95 ºC, and that the absorber temperature is maintained at 35 ºC respectively

For these two chillers, determine
i) The refrigeration effect and the mass flow rate of the refrigerant
ii) The energy input at the compressor / the generator
iii) The coefficient of performance (COP)
For the centrifugal chiller, determine
iv) The condenser water flowrate
v) The water cooling tower coefficient (make your own assumption of the cooling air flowrate)

For the absorption chiller, determine
vi) The concentration and mass flow rate of the weak and strong solution respectively
vii) The mass flow rate of the condensing water if the same condensing temperature is to be maintained at 32ºC and 38 ºC. Determine the inlet and outlet temperature of the water through the absorber and the condenser if the water first passes through the absorber then the condenser.
Attach with your answer the charts and/or diagrams that you have used in the calculation. State any engineering assumptions taken.

Solutions

Expert Solution

We need P-H chart for Two chiller to solve the problems. I have defined some terms which will be helpful to calculate the necessary requirements.

One TR is the amount of cooling obtained by one ton of ice melting in one day i.e. 12,000 Btu/hr, 3024 kcal/hr or 3.516 thermal kW.

Net refrigerating capacity • A quantity defined as the mass flow rate of the evaporator water multiplied by the difference in enthalpy of water entering and leaving the cooler, expressed in kW, Btu/hr, kcal/hr, or tons of refrigeration.

kW/ton rating • Commonly referred to as efficiency, but actually power input to compressor motor divided by tons of cooling produced, or kilowatts per ton (kW/ton) • Lower kW/ton indicates higher efficiency • kW/TR as a reference energy performance indicator •

Coefficient of performance (COP) • Chiller efficiency measured in cooling output divided by electric power input.

• Energy efficiency ratio (EER) • Performance of smaller chillers and rooftop units is frequently measured in EER rather than kW/ton • EER is calculated by dividing a chiller's cooling capacity by its power input at full-load conditions • The higher the EER, the more efficient the unit. P-H chart of centrifugal chiller below....

Efficiency = Useful energy output/ Energy input = Useful power output/ Power input

genius_generous answered 1 year ago

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