Heat Definition and 1000 Threads

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...

Please, i need help

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...

Hello everybody, would somebody please put me on the right track to answering this question? 'Consider water undergoes a heat transfer at constant pressure of 10 MPa and changes from liquid to steam. Find the entropy of the system (sfg) as well as the heat transfer per unit mass in this...

The answer key says the work done should be +.043cal. I am getting a negative sign. I have posted my work in the attached image. My logic is that since this a reversible engine we can say the integral of dQ/T=0. Looking at the cycle, Qc isi being absorbed (Qc>0) and Qh is being rejected...

My book states the answer to this problem is . I have gotten very close to the answer. My problem is my Tc/th and tc/tm are flipped compared to the solution. I feel like I am missing something in my algebra but can't see where I am going wrong. Could I get some help identifying where my...

What I understand is that the β parameter of the npn transistor is temperature dependent. Increasing the temperature increases the collector current and hence the LED turns ON. But I don't understand the resistor arrangement.Also I can see that the diode is keeping the Base-Emitter junction in...

The question & my solution

Hello, I am a final year mechanical engineering student designing a heat pump with a linear compressor for an electric vehicle and have decided to model this using Simulink, I would love some help on the governing equations/formulas needed for each component of the heat pump as well as guidance...

a.)I would say the stirring, a form of mechanical work, is increasing the internal energy of the liquid, releasing heat into the system, which thereby raises the temperature. b.) Work is obviously being done by stirring the liquid. c.)Well we are doing work on a system so W>0 and with the...

Hi, I have been calculating a series of hypothesis for some aquariums/tanks situations, using heat transfer equations (conduction, convection, radiation, evaporation) Typically we have aquariums that run at higher temperatures than the surroundings in winter and lower temperature than the...

Hi, I've checked the literature but couldn't find any formulas or examples for this particular problem involving heat sink with straight fins: As you can see, I want to assume: - power at the bottom surface - convection (known ambient temperature and heat transfer coefficient) at the...

At first, I tried to calculate the heat energy required by doing this: I realized I should calculate heat energy separately instead of grouping glass and water together so I did this: But the answer is supposed to be 6.29 x 10^4. I don't know how to solve this. Can anyone help please? Thank you

My work Q= 0.025 * 4190 * (34-100) = -6910 but on chegg but did they do Q= 0.025 * 4190 * (100-34) = 6910. I thought the initial is 100C and final is 34 because it goes from 100 to 34

One has two same volume blocks of metal, one Aluminium and one copper pushed together. If the Aluminium is instantly heated to 100 degrees C, since it has significantly higher heat conductivity will the copper draw the heat out and at some point be hotter then the aluminium? Or will it just draw...

My thought process of how i do the ice melting part: (note I just ignore the copper/lead part cause I already know how to do that part) Q_ice + Q_melt + Q_liquid so, it 0.018(2100)T+0.16(4190)T+0.018(334*10^3) but on chegg they didn't use 2100 but they just use 4190 instead and I am confused...

Something that has been on my mind a while. If a CCGT generates electrical power at 64% efficiency, and a COP4 heat pump, powered by that generator, generates 4 times the thermal power to electrical power, wouldn't that mean we can get 256% heat out of the fuel's calorific value? Maybe that is...

Dumb question. Is there a direct heat energy relationship between a heated object and infrared radiation? 1 to 1 relationship? Or can IR go up without there being much heat?

Looking for the best material for a heat exchanger exposed to vacuum in a space ship. I've initially gone with radiator vanes that are a ceramic blend and typically operate at twenty-five hundred degrees, but then I started wondering if there is a better material...and now I'm here, hoping for...

how to show or prove that the shape of the solution of a heat equation can only go smoother and smoother but not the opposite as time increases?

Hello, I'm just wanting to make sure I remember this correctly. I have a hot exhaust pipe I want to shield from fuel lines. So I have a shield (stainless) that is going 1/2 way around the exhaust, with an air gap of about 1". I want to sand blast the side facing the heat and polish the side...

Hi, starting for this thread Question about entropy change in a reservoir consider the spontaneous irreversible process of heat transfer from a source ##A## at temperature ##T_h## to another source ##B## at temperature ##T_c## (##T_h > T_c##). The thermodynamic 'system' is defined from sources...

Through an intriguing fictitious dialog between Sadi Carnot and Robert Sterling, Prof. Israel Urieli of the Ohio University shows that it is not required to invoke entropy, the second law of thermodynamics, and the Carnot cycle with the [ideal] adiabatic processes in order to find out the...

I have checked several textbooks about the heat equation in a rectangle and I have found none that deals with my exact problem. I have though to use separation of variables first (to no avail), then Green's function (to no avail), then simplifying the problem for example by defining a new...

In working out the Clausius-Clapeyron equation in an elementary method, we usually consider the work done in a Carnot cycle, built with two isothermobarics at ##p## , ##T## and ##p- dp##,##T-dT## pressures and temperatures and two adiabatics, as ##\mathcal{L} = dp(V_g - V_\ell)##, where ##V_g##...

ΔTLMTDcf = 20 - 30 ln20/30 ←(What is "In"?) = 24.7°C ←(Why the answer is 24.7? How?)

If I look at the specific heat equation mentioned, then I would be inclined to think that without heat energy being added to the gaseous mass its temperature cannot rise. But, if some form of energy like chemical energy in gaseous mass could be directly converted to internal energy of the same...

A drop of fuel is ignited in an engine cylinder, that produces heat, light and sound energies from the chemical energy stored in the drop of oil. What I am not clear about is how heat energy gets transformed into mechanical work? I think the heat energy produced from ignition flows from burnt...

Let's say we have a cylindrical fuel pin with fissile material in the middle, followed by a gas gap and cladding material. It is being cooled by water on the outside. The temperature drop through the fissile material should be parabolic due to heat generation, and the temperature drops through...

Given a 1D heat equation on the entire real line, with initial condition ##u(x, 0) = f(x)##. The general solution to this is: $$ u(x, t) = \int \phi(x-y, t)f(y)dy $$ where ##\phi(x, t)## is the heat kernel. The integral looks a lot similar to using Green's function to solve differential...

Can we make sense out of the formula of entropy like we do for density (like "quantity of mass per unit volume")? What's the sense of Q/T? Couldn't it be something else? Of course it probably is a 'me-problem', but I haven't studied Thermodynamics deeply yet and was wondering what Entropy...

So the formula for power is Power = work / time. There's two types of energy transfers: heat and work. How do you calculate the power of something using heat energy in BTU/hr when BTU isn't work?