Now that I have collected my data I am going to calculate the rate of heat transfer by using the following formulas:
Energy input = ITV
I = Current
T = Time
V = Volt
Energy output = mCΔT
m = Mass
C = Specific heat capacity
ΔT = Temperature change
Electricity to heat
Energy input: I = 5 × T= 302 × V=7.5
= 11325
Energy input = 11325 (J)
Energy output: m = 100 × C = 4.2 × ΔT = 13
= 5460
Energy output = 5460 (J)
Gas to Heat
The calorific value of British gas is 39.5kJ kG-1and I have used 320g of British gas.
Energy input: 320 × 39.5
= 12640 (J)
Energy input = 12640 (J)
Energy output: m = 101 × C = 4.2 × ΔT = 13
= 5514.6
Energy output = 5514.6 (J)
Also I have been asked to calculate energy from Electricity to Kinetic of the following question:
Case study: A laboratory lifts uses an electrical motor to raise a carriage which weighs 35KN, through a vertical height of 10M at a steady speed, If the motor uses a current of 30amps at a potential difference of 450 and runs for 30sec.
Q1) How much work must it do?
A) The following equation is used for work done: W = FD
Work done = Force (N) × Distance (M)
As force is given as kilo Newton which means I would have to convert it
in order to get Newton by multiplying KN by 1000.
KN = 35 × 1000 = 35000 (N)
35000 (N) × 10 (M) = 350000 (J)
= 350 (KJ)
Q2) How much electrical energy does it use?
A) The following equation is used for electrical energy: E = ITV
Electrical energy = I (amps) × T (sec) × V (volts)
30 (amps) × 30 (sec) × 450 = 405000 (J)
= 405 (kJ)
As I have achieved to calculate the amount of energy given in and used I am able to calculate the efficiency of energy by using the stated formulas below:
Energy efficiency is the ratio between the useful output of an energy conversion machine and the input, in energy terms. The useful output may be electric power, mechanical work, or heat. Energy efficiency is not defined uniquely, but instead depends on the usefulness of the output. All or part of the heat produced from burning a fuel may become rejected waste heat if, for example, work is the desired output from a thermodynamic cycle.
Electricity to heat
Input energy = 11325 (J)
Output energy = 5460 (J)
5460 ÷ 11325 × 100 = 48%
Energy efficiency = 48%
Gas to heat
Input energy = 12640 (J)
Output energy = 5514.6 (J)
5514.6 ÷ 12640 × 100 = 44%
Energy efficiency = 44%
Electricity to Kinetic
Input energy = 405 (kJ)
Output energy = 350 (kJ)
350 ÷ 405 × 100 = 86%
Energy efficiency = 86%
By looking at the stated results above I am going to make a judgment that energy from electricity to kinetic is more efficient where as electricity to heat is lesser efficient in this particular project and the reason for that is because when the gas is turned on from its source some of its energy loses in the air or losses energy where the Bunsen burner freshly turned on and it takes some time to heat it up while the energy is wasting.
As well as electricity to heat loses its energy when the electric device produces light and sound as waste energy. There are many pros and cons to consider when it comes to choosing between a gas heat transfer and electric heat transfer for any particular task. They both can be pretty efficient in their own way.
The down side of gas heat is in the name itself. The gas heat depends on fossil fuels to stay alive. The problem with that is most likely going to be the surge in prices when fossil fuels are in short supply. This can cause the bill to rise well over.
