Energy saving per degree increase in temperature
Energy saving per degree increase in temperature
(OP)
Hi,
I am designing a heat recovery system for a milk powder spray drier. I will be utilising waste exhaust heat (67degrees C 245T/hr) and use it to pre heat the inlet air to the drier.
The drier inlet air is supplyed at 35degees C where it is then heated to 205degrees C by an air heater (160T/hr). The air is then used in the drier.
I will be putting a heat exchanger in the exhaust and in the inlet prior to the air heater.
I am wanting to do some initial energy calculations to determine viability. I would like to know the energy saving (and cost saving) that will be obtained for every degree Celcius I pre heat the inlet air before the air heater. Given an energy cost of $0.12 per kWh.
Can anyone help with these calculations?
I am designing a heat recovery system for a milk powder spray drier. I will be utilising waste exhaust heat (67degrees C 245T/hr) and use it to pre heat the inlet air to the drier.
The drier inlet air is supplyed at 35degees C where it is then heated to 205degrees C by an air heater (160T/hr). The air is then used in the drier.
I will be putting a heat exchanger in the exhaust and in the inlet prior to the air heater.
I am wanting to do some initial energy calculations to determine viability. I would like to know the energy saving (and cost saving) that will be obtained for every degree Celcius I pre heat the inlet air before the air heater. Given an energy cost of $0.12 per kWh.
Can anyone help with these calculations?





RE: Energy saving per degree increase in temperature
http://www.engineeringpage.com
Go under heat exchangers ...
http://www.engineering-4e.com
RE: Energy saving per degree increase in temperature
specific heat of air room temp = 1.012J/g.K
(1 degree C)* (1.012)*160000000
= 161920000J
1kWh = 3600000J
44.98kWh = $4.5
at $0.1 per kWh
There for will be saving $4.5/hr for every degree the inlet air is pre heated.
Are these calculations correct??
RE: Energy saving per degree increase in temperature
I think I have it right except I was using cost for electrical energy not thermal.
Given the milk powder plant has a co-generation plant on site I am costing according to steam energy prices.
1 tonne of steam = $15NZD
1 tonne of steam = 665kWh
Therefore cost = $0.0232 per kWh
giving a energy saving of $1.04NZD/hr if the inlet temp is increased from 35 to 36 degrees C.
Pretty sure this is correct, hopefully it may help someone else interested.
RE: Energy saving per degree increase in temperature
I did get a chance to notice that initially something was kind of fishy with some of the units used ...
It is very good that you are reporting your final output values. In my opinion, it demonstrates that you are serious and do get to the final step of engineering calculations.
http://www.engineering-4e.com
RE: Energy saving per degree increase in temperature
RE: Energy saving per degree increase in temperature
I managed to get hold of a Mechanical engineering handbook (Energy volume) which has proved very useful.
I don't however understand how the dew point will effect the heat recovery process. Because I am only preheating the air before the air heater. There are no combustion products in the exhaust stream.
Am I miss understanding something?
RE: Energy saving per degree increase in temperature