In thermodynamics, heat is energy in transfer to or from a thermodynamic system, by mechanisms other than thermodynamic work or transfer of matter. The various mechanisms of energy transfer that define heat are stated in the next section of this article.
Like thermodynamic work, heat transfer is a process involving more than one system, not a property of any one system. In thermodynamics, energy transferred as heat contributes to change in the system's cardinal energy variable of state, for example its internal energy, or for example its enthalpy. This is to be distinguished from the ordinary language conception of heat as a property of an isolated system.
The quantity of energy transferred as heat in a process is the amount of transferred energy excluding any thermodynamic work that was done and any energy contained in matter transferred. For the precise definition of heat, it is necessary that it occur by a path that does not include transfer of matter.Though not immediately by the definition, but in special kinds of process, quantity of energy transferred as heat can be measured by its effect on the states of interacting bodies. For example, respectively in special circumstances, heat transfer can be measured by the amount of ice melted, or by change in temperature of a body in the surroundings of the system. Such methods are called calorimetry.
The conventional symbol used to represent the amount of heat transferred in a thermodynamic process is Q. As an amount of energy (being transferred), the SI unit of heat is the joule (J).
Hello,
I am stuck how to proceed with the equations below.
The problem:
A tank containing ##m_0## mass, with a temperature of ##T_0##, is to be filled with a total mass of ##m_1##, with the constant mass flow rate ##G## and temperature ##T_1## during ##t_p## seconds. ##T_0>T_1##. Other than the...
photo below... Is it possible to make a machine that would take more heat from the hot reservoir to do work than what would hot reservoir give to the cold reservoir(heat)? Apparently, it's impossible because it violates 1st law of thermodynamics.
the thickness of the arrows symbolizes the...
Consider the following heat map:
from scipy import special
import numpy as np
import matplotlib.pyplot as plt
u0=200
r0x=25
r0y=25
rmax=2.5
alpha=2
t=0.575
y, x = np.meshgrid(np.linspace(0, 50, 100), np.linspace(0, 50, 100))
r=np.sqrt((x-r0x)**2+(y-r0y)**2)...
https://en.m.wikipedia.org/wiki/Heat_death_of_the_universe
Is the heat death of the universe completely unavoidable in an universe with an accelerated expansion dominated by dark energy like ours?
Or can there be any way to avoid it according to current knowledge, observations and experiments...
Interesting optimization concept, to increase the size of the heat shield significantly to reduce the heat stresses during reentry...
https://www.cnn.com/2022/11/17/world/loftid-heat-shield-nasa-success-scn/index.html
If I know the standard of the steal I have let's say ASTM A709 grade A how do I determine the temperature and time necessary for any heat treatment to be done on it?
In defining the heat capacity of a subatance as the constant relating change in temperature to change in heat, is it assumed that the system does no work? Does it really say (heat capacity is the constant relating heat change to temperature change when the system does no work)?
I had an idea thinking about heat transfer and how placing water over a hot surface will transfer the heat to the water. It got me thinking, in a case where water could not be an option for a medium could I use metal, which would still have a higher heat transfer to absorb more of the heat...
I have a solar water heater on my deck, with a circulator powered by PV, that pumps heated glycol through a wand heat exchanger placed in an 80 gallon tank. Water comes from the well's pressure tank, passes through this solar pre-heater tank, then into an LPG heater that adds any heat needed. I...
Hi, cannot get a definite answer anywhere on how heat transfer occurs with this fluid. All that the manufacturer gives is "excellent heat transfer". Water has excellent heat transfer due to convection currents. Need to know if this fluid also heats by convection rather than conduction...
***A Carnot Engine*** is a theoretical engine unlike a Sterling Engine which can be made practically.
Some of the drawbacks of Carnot Engine are,
1)The Heat Transfer occurs only during isothermal process(compression and expansion),this is because the working material (ie) gas or fuel used, if...
I am going through these notes...they are pretty easy to follow. I would like more insight on the initial condition. In this problem, (attachment below), i guess the choice of initial condition is convenient as its easier to plug in the values of ##n=2## and ##b=3## (highlighted on the...
Hi I'm doing my extended essay (like a research paper) for the IB and I'm having a bit of trouble with my setup and data process. The plan for my experiment goes something like this: I have a magnet wrapped in wire strapped to a battery and a superconductor in liquid nitrogen. After levitating...
I have always had trouble with formulas. Now the trouble is about a definiton. I would like to ask you how accurate the definition of heat is. It does not seem to me completely accurate. I think it is partly accurate.
From the Fundamental of Engineering Thermodynamics by Sonntag\Borgnakke...
Hi guys, I'm a 2nd year mechanical student currently taking heat and mass transfer. A question came up in my mind when I was looking into the conduction heat transfer.
If I put block B on block A where block A is 573K and block B is 303K. Is there any way that I can calculate the time required...
I was reading posts this morning on another forum and came across a question that made me start thinking about physics. Since I've always tried to satisfy my curiosity through reading and trying to learn new things, or trying to remember the things that I've forgotten years ago, I went to...
I don't like to put holes in the cabinet surfaces in my RV. To attach things to the surface of a cabinet I recently used velcro tape,one side on the cabinet surface, the other side on the lightweight thing I want to attach. I like being able to remove the attached thing and replace it as...
There are different ranges of IR. Are they all represented as heat? If not maybe Webb telescope can read those only so our own sun isn't as much of an obstacle? Maybe xray instead?
I have been given the task of modeling the heat transfer from a light source of known power into a system consisting of two connected materials. I must find the temperature change in the bottom surface. The two materials are initially in thermal equilibrium with the surroundings.
My first...
Hello :
i was watching the news , and it was all about how Europe will start the coal factories again for energy generation
had a question related to reduction of coal consumption for energy generation
1 ) could we use coal fine particles instead of chunks of coal that will burn more...
Hi. I'm an amateur mason - I currently use drills and plugs to split granite boulders. I've used sledge hammers, chisels and levers. I've dropped rocks, used hydraulic presses and tended fires to crumble and split rock. It's hard work. It's long hour work.
I'm wondering if there's not a better...
Hi,
I'm going to make a comparison test between Photovoltaic solar panels and the radiator type.
I intend to store all heat with an insulated water tank.
Many years ago, I heard about water bottles in a green house with some kind of salts in the water, which allowed the water to store more...
During a thermodynamic cycle, an ideal thermal machine absorbs heat Q2 > 0 from a hot source and uses it to perform Work W > 0, giving a cold source a heat Q1 < 0 with an efficiency of 20% . How much is the work done as a function of Q1 ?I have 2 question regarding this problem: 1) Why is Q1 the...
I believe that just using the equation above should yield the following:
R_{tot} = \frac{18 -(-5)}{400 + 2(80)} = 0.041
but the units don't seem to match up... The units of the above answer are in K / W.
Is there a different formula i should be using?
Your help is appreciated!
Good morning,
I have a 90 mq house burning 1200 smc of methane every year.
I live alone and i keep 20°C when I'm at home (evenings) and 18.5°C when I'm not.
My window frames are quite old, and I don't know very well if it's the case to spend 8 monthly payments to update my hardware.
What is...
So I'm looking at the book "Equilibrium Statistical physics" by Plischke and Bergersen. I'm doing the calculation of the specific heat of the 2D Ising model. I can't seen to quite get out the same expression as in the book - there are a coupe of minus signs that are different. I don't know if I...
Hello Forum,
I write you with the challenge of calculation the heat dissipation of a LED.
The LED in question is http://www.seoulsemicon.com/en/product/spec/SZ5-M3-W0-00/22
a download of the datasheet is possible.
The LED binning is 290lm (W4, 5000K) at 700mA, the efficacy is...
Hello,
I am trying to figure out if the investment into a watercooling system in a Cosplay suit would be worth it.
I plan on using a water loop made by taking a "CoolShirt" https://coolshirt.com/product/white-coolwater-shirt/ and running water through it either from an ice bath in a sealed...
So heat pumps are an interesting thing which I've recently discovered, and it has led to curiosity about how they work and what you can do with them. I hope to make my own property at some point, so a heat pump will doubtless come up then as I would like it to be an eco-home.
Ground source heat...
Hi!
I need to calculate what air flow needs to flow across the condenser so that the heat emitted from the condenser is directed to the air.
dT=10÷15 [C]
COP =~3
According to the manufacturer's data the fan airflow is 0.67 [m^3/sec] and i need to check if i can use it.
thanks
Hello,
I have the following problem and hope you can help me. I have the setup as shown in the drawing. A pipe that is flowed through, and in the middle of it another pipe, but at the end of this branch is a sensor. Initially the fluid would flow, with a temperature of 25°C. If my thought is...
I had seen a few topics from this forum while searching for information on the temperature differential possible in a reverse polarity thermocouple junction. I was reading some of the replies and I am wondering if the heat pump is understood.
It uses a refrigerant that can be anything that...
Hi, I am solving heat equation with internal heat sources both numerically and analytically. My graphs are nearly identical but! analytical one have problem at the beginning and at the end for my domain. Many people have used the same technique to solve it analytically and they got good answers...
At very high temperatures CO2 should have Cp = 15/2 R, since there are 3 translational, 2 rotational and 4 vibrational degrees of freedom.
Experimental values are a bit higher than that, at least according to a figure I found on the internet.
Is that correct? And what is the explanation?
A...
https://news.mit.edu/2022/thermal-heat-engine-0413
This team that developed this device claims it is capable of generating electrical current from a 1900C heat source via the photovoltaic effect.
I was wondering if the generated electricity was put through an initially 1901C electrical...
Can someone walk me through this? Our teacher didn't bother to meet us synchronously ever since and I'm kinda stumped on solving this. The equation I used for this problem is:
mi = [mw(cw)(ti-tf)]/[Lfi + (Tf - Ti)]
mi = [190(1)(23-3)]/[79.6+(3+20)] = 37.04g
mi = mass of ice
mw = mass of...
Since the heat of formtion of H2O is -285.8 and the heat of formation of CO2 is -393.5 I thought that the heat of reaction CH4 + 2O2
should be -393.5 + 2(-285.80 = -965.1
Where am I wrong?
I am doing a project, actually it is a simulation. And we aim to determine the spatial and heat flux evolution of the system. The system consists of two concentric cylinders separated by an insulating material. I change the value of kappa of the insulator but the heat flux remains always the...
My understanding of why Mars lost its atmosphere was because it cooled down too much internally and that when this happened, the planet lost its magnetic field that helped protect it from solar winds (which then ended up stripping away the planets atmosphere). Is there anything that people could...
Consider mixing ice water with the hot water and vice versa so that the two reservoirs are closer to the same temperature. What will happen to the mechanical/thermodynamic efficiency and ideal Carnot efficiency of a heat engine?
Can I understand that light energy contains heat energy?
or Do I have to separate between two concepts? because light energy from the sun makes heat energy after absorption of molecular?
By chance, I have read a paper that left me in shambles. I would like you to help me figure out if it makes sense or not. I tried to follow Bridgman's logic, without a complete success. The extraordinary claim is that, if you start with a system consisting of a 1cm^3 copper cube where 2 faces...
A class project requires us to model the Otto cycle using ideal gas properties. We are not given the value for qin (specific heat in) and are told to make an intelligent approximation. My approach to this has been to find the calorific value of petrol, multiplying this by the density of petrol...
Homework Statement:: First of, this is not a "homework" per say, since this is not in my curriculum. If you still want to help, see the description :)
Relevant Equations:: C = Q/(delta T), where delta T is the raise in temperature in Kelvin and Q is the added heat energy
I want to learn about...
If I was to bore a 4" or even 6" diameter hole into my garage floor drain and install a PVC pipe to a depth of 10 feet would the geothermal heat keep my garage warmer? I live in Northern Michigan and frost can reach depths of 7' or more. I am not looking to sweat in there, but could it allow...
I am trying to find the specific heat (at constant pressure) ##C_p## coefficients linked to the JANAF model, which basically assumes that ##C_p## is a polynomic function of ##T##, for liquid nitrogen (at ##\approx## 97 K).
Before doing that, I am trying to find those for water (at ##\approx##...
The household LPG burns with a blue flame. There's nothing to prove!
But what if we attempt to do that? How do we go about it?
I started with the assumption that it is a complete combustion of the LPG. A Google search tells me that the calorific value (the amount of heat a substance gives off...