Question bank for Energy Managers & Energy Auditors
Evaluate heat rejection (kCal/h) of each heat exchanger and total heat rejected to cooling water.
Heat
exchanger
Water flow, m
3
/h Temperature
raise, °C
Heat
rejection,
kCal/h
1 200
7
14,00,000
2 300
8
24,00,000
3 400
3
12,00,000
4 500
2
10,00,000
60,00,000
2.
Define specific power consumption with an example.
The specific energy consumption is defined as the energy required to produce a unit of output.
e.g. : Compressors:
A compressor generates 100 cfm of air at 7 kg/cm
2
pressure. The power drawn by the motor is 18
kW.
i.e. Specific energy consumption is
= 18/100
= 0.18 kW/cfm @ 7kg/cm
2
3.
Why Sankey diagram is useful in energy balance calculations?
The Sankey diagram is very useful tool to represent an entire input and output energy flow in any
energy equipment or system such as boiler generation, fired heaters, furnaces after carrying out
energy balance calculation. This diagram represents visually various outputs and losses so that
energy managers can focus on finding improvements in a prioritized manner.
4.
List any three guidelines for mass and energy balance.
• For a complex production stream, it is better to first draft the overall material and
energy balance.
• While splitting up the total system, choose, simple discrete sub-systems. The process
flow diagram could be useful here.
• Choose the material and energy balance envelope such that, the number of streams
entering and leaving, is the smallest possible.
• Always choose recycle streams (material and energy) within the envelope.
1.4 Material and Energy Balance
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