System efficiency is the keyword . The concept of using a refrigeration plant for the production of hot water may seem to defy logic . On closer inspection , the simplicity of the system reveals on untapped energy source .
INCORPORATING COLD CHAIN
CONTRIBUTORS
Saving with heat recovery = optimum plant efficiency = system calculation
By Isolde Dobelin , director at Open Trade Training Centre ( OTTC )
System efficiency is the keyword . The concept of using a refrigeration plant for the production of hot water may seem to defy logic . On closer inspection , the simplicity of the system reveals on untapped energy source .
A
heat recovery system uses heat from the condenser of a refrigeration plant . The recovered heat is used for water heating or other heating purposes . The operation and economy of the plant is not affected . The heat required to heat the water is already there – no additional energy needs to be expended . Money , money , money … The technical aspect of heat recovery will not be discussed at this point . What follows is a closer look at the energy saving potential of the system . The case study of a medium sized butchery will serve to demonstrate the calculation . Said butchery uses 1 200l of hot water per day . This water is heated by means of a conventional geyser with an electrical heating element .
The annual cost of heating the water is calculated as follows :
To begin with , the electricity consumption ( Watt ) needs to be established .
Example :
Qs = Heat Capacity in W ( Watt ) or kW ( kilo Watt ) Dt = Temperature difference between cold water in and hot water out in K ( kelvin ) V = Volume of water C = Specific heat of water
Formula :
Qs = V x C x Dt 18 ° C = Cold water in 60 ° C = Hot water out
Dt = 42K
Qs = 1 200 x 1.16 x 42
Qs = 58 464 W or 58.464kW The assumed electricity rates in rand per kW x R / kW :
Cost = 58.464 per day x R 0.40 incl . VAT Industrial Rate Cost = R 23.39 per day x 30 per Month = R 701.57 Cost = R 701.57 x 12 per year = R 8 418.82 saving
Now we establish the amount of water that can be heated by means of the heat recovery system :
Here we assume that the power absorbed by the compressor is 4kW of the normal discharge temperature as the condenser lies between 70 ° C and 75 ° C . This means that the refrigeration plant provides 4kW of energy per hour which can be utilised to heat up the water . If the refrigeration plant ’ s operating time is 16 hours per day , then 82 x 16 = 1 372l of water
© Eamonn Ryan / Cold Link Africa .
Isolde Dobelin , director at Open Trade Training Centre ( OTTC ).
can be heated per day , free of charge . This calculation depends on the local residential rate compared to the use of a heat pump system for heating and cooling the house , as well as using hot water for the pool .
Cost = 58.464 per day x R 2.89 incl . VAT Residential Rate Cost = R 169.49 per day x 30 per month Cost = R 5 084.70 per month x 12 per Year = R 61 016.40 saving . CLA
The case study of a medium sized butchery will serve to demonstrate the calculation . Said butchery uses 1 200l of hot water per day .
COLD LINK AFRICA • June 2023 www . coldlinkafrica . co . za 31