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I was wondering if anybody could help with a couple of question from the 2005 Craftsman Gas exam,
1......'state three basic safety requirements specified in the building code to be considered when designing gas-piping systems for installation in buildings?'
2.....''Calculate the gas input rate in m3/h for an instantaneous water heater with the following specification,
Max water flow.... 15l/min
water inlet temp....12 degrees
water out temp.....40 degrees
Specific heat capacity....4.2 kJ
Heater efficiency....75%
Heating value of gas..... 40mj/h
any help would be greatly appreciated!~ cheers
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here is the answer I came up with, and explanations to my method for following, this can be used to find the heating for room heaters also.
work our the heat input to the water knowing that 4.2kj is needed to heat 1 litre of water 1 degree Celsius.
So 15 l\min is 900 l\hr helps for this
900 l\hr x 4.2kj x 28 degree temp rise =105840 kj\hr. can be changed to 105.84 Mj\h
the input to the appliance, use the efficiency = output/input, so change the equation to suit.
Input to the appliance is 105.84 M\hr / 0.75 = 141.12Mj\h.
the formula that I used to calculate gas through a meter is : m2 = mj\h x cv x 3600 / time(sec) if you like to know.
gas rate is 141.12mj\h / 40 =3.528 m3\h
Hope this is useful and correct. I would be interested also if anyone has another method so I can be enlighten too
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cool thanks mate