How many joules of heat will be delivered to the room

In summary, the coefficient of performance for a heat pump is the percentage of the energy that is delivered to the room for each joule of electrical energy consumed.
  • #1
name_ask17
146
0

Homework Statement


In a heat pump, heat from the outdoors at -8.00 deg c is transferred to a room at 22 deg c, energy being supplied by an electrical motor. How mnay joules of heat will be delivered to the room for each joule of electrical energy consumed, ideally?


Homework Equations


Q=mcT?
im not sure about this one




The Attempt at a Solution


i tried the mcT, but that did not give the the correct answer. The answer should be 63.6% (answer given by instuctor) please help.
 
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  • #2


The question is asking for the coefficient of performance of the heat pump. Do you know the expression for COP?
 
  • #3


Q/w correct? and if yes, what equation would i use to find heat, and how would i apporach the work?
 
  • #4


Yes, that's the correct expression. But how would you express the ideal coefficient of performance for a heat pump in terms of the temperatures. Look it up!
 
  • #5


i found that Q=Winput+Qc
but the problem does not state an input.
 
  • #6


name_ask17 said:
i found that Q=Winput+Qc
but the problem does not state an input.
"...for each joule of electrical energy consumed" is the input. Find the coefficient using the temperatures.
 
  • #7


to do that would i use Qh/Qh-Qc?
 
  • #8


Where are the temperatures?
 
  • #9


outside= 266K
and inside= 295K
so the hot would be the inside and cold would be the outside?
 
  • #10


im still a little confused
 
  • #11


Look up an expression for the coefficient of performance for a heat pump in terms of the temperatures.
 
  • #12


all i am finding is the hottemp-coldtemp/hottemp
is that not correct? it is not giving me the answer
 
  • #13


i am very lost.
 
  • #14


i am not grasping the concept. can you please explain to me step by step what i am doing wrong. am i even using the right equation? if not, then i do not know what equation to use. i have to know this by tonight and i have the answer...just don't know how to get there. 63.6% is the answer. but why?
 

Related to How many joules of heat will be delivered to the room

1. What is the formula for calculating joules of heat delivered to a room?

The formula for calculating joules of heat delivered to a room is Q = m x c x ΔT, where Q is the heat energy in joules, m is the mass of the substance, c is the specific heat capacity, and ΔT is the change in temperature.

2. How do I determine the mass of the substance for the calculation?

The mass of the substance can be determined by either measuring the weight of the substance or by using its volume and density. The formula for mass is m = ρ x V, where ρ is the density and V is the volume.

3. What is specific heat capacity and how do I find it?

Specific heat capacity is the amount of heat energy required to raise the temperature of 1 gram of a substance by 1 degree Celsius. It is measured in joules per gram per degree Celsius (J/g°C). Specific heat capacity values can be found in reference tables or by conducting experiments.

4. Can you provide an example calculation for determining joules of heat delivered to a room?

Sure, let's say we have 2 kg of water (m = 2,000 g) and we want to raise its temperature from 20°C to 60°C (ΔT = 40°C). The specific heat capacity of water is 4.18 J/g°C. Using the formula Q = m x c x ΔT, we can calculate: Q = (2,000 g) x (4.18 J/g°C) x (40°C) = 334,400 J. Therefore, 334,400 joules of heat will be delivered to the room.

5. Are there any other factors that may affect the calculation of joules of heat delivered to a room?

Yes, there are other factors that may affect the calculation, such as the type of material used to heat the room, any heat loss through insulation, and any changes in temperature or mass during the process. These factors should be taken into consideration to get a more accurate calculation.

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