Heat transfer Definition and 875 Threads

Homework Statement One of the two glass panes in each window is coated with a transparent electrical conductor. Why does this coating improve the window's insulating ability? Select one: a. The transparent conductor is black in the infrared, with a low-temperature emissivity of almost 1. b...

In my heat transfer course, I always had to do analysis of long-wavelength radiation between surfaces first, and find the heat radiated from one of the surface. Then, solar radiation is added to the problem, and suddenly it was said that solar radiation=heat radiated from this surface! Does...

I am doing an assignment about heat energy transfer and passive cooling. I understand that heat energy is transferred into rooms through windows by conduction, but I'm confused about if heat energy is also transferred through windows by solar radiation and where infrared radiation comes into...

Hi, I have been trying to set up a funtcion of the temperature over time and I am doubting my results. In the system i have: Fig 1. The system is at rest. For simplicty I've considerd the ambient temperature to be same as T1. By knowing: Fig 2. yeilds: Fig 3. In my case B&C is at a...

Homework Statement n moles of gas, that follow van der Waals equation are to be employed as the auxiliary system in a circular cycle(parameterized using T_h and T_c as shown on the TS diagram. Calculate the efficiency of the cycle. Homework Equations , , Q = TdS The Attempt at a Solution...

My book states that Heat and work represent energy in transit. The state of the system undergoes a change after heat is supplied to it and before work is extracted from it because energy gets stored in it. My doubt is here that ,heat has been transferred to the system and it says heat is energy...

Homework Statement [/B] Hi guys. Been looking at this question for a while and can't figure it out. An aluminium furnace is fuelled with propane gas. The furnace is loaded up with 4 aluminium ingots each of mass 22.5 kg. The question is: If 2.1 kg of propane is used to complete the melting...

Hi there, Hopefully this is a very easy question and you all can just confirm this for me. When calculating heat transfer into a fluid from a heated tube, is it correct to say that the heat transfer coefficient is *not* dependent on the tube diameter? So, if we solve for T_{out}, we get...

Hi! Basically I have some tasks in thermodynamics calculating the heat transfer through a wall. I have been attempting to solve the following problem: “Calculate the heat transfer through the exterior wall in a building, where the temperature inside the building is 20 °C and the temperature...

In context of heat transfer, are conduction and diffusion same process?

Hello, I'm currently taking some summer classes at my college and was assigned a project to transport vaccines from one location to another (travel time ~2-5 hours.) We have to keep the vaccine within the range of 35-46 degrees Fahrenheit at all times. My group and I came up with the idea of...

My book states that when a flow around object is considered, Non dimensional momentum flux is defined as the drag coefficient In case of flow through tubes it states The non dimensional momentum flux is defined as the friction factor What do these statements mean? What do they practically...

Homework Statement A 5m long heated pipe is used heat up water from 15°C to 65°C. Water flow through the pipe is 10liter/min. The heating gives a constant heat flow in all parts of the pipes surface. The inner and outer diameter of the pipe is 30 and 50 mm, respectively. Calculate the heat...

Homework Statement I am confused on how it's using the surrounding temperature minus the surface temperature as its the other way around in the Newton's law of cooling, Doing that would change the sign of convection right? I don't see the reason to do that, since if left side is hotter, then...

Homework Statement (I) Explain what is meant by an 'overall heat transfer coefficient'. (II) Explain what is meant by fouling and what its effect will be on the value of the overall heat transfer coefficient. 
 Homework Equations None provided. The Attempt at a Solution (I) The overall heat...

Homework Statement One end of a solid cylindrical copper rod 0.200 m long and 0.0250 m in radius is inserted into a large block of solid hydrogen at its melting temperature, 13.84 K. The other end is blackened and exposed to thermal radiation from surrounding walls at 500.0 K. (Some telescopes...

Assume we have a cylindrical fin which has the effective length of L and its efficiency is given by the equation: $$η=exp(-0.32mL)$$ where $$m=\sqrt{\frac{hP}{kA}}$$ where P is perimeter and A is the cross sectional area of the fin. If the volume of the fin remains constant, which of the...

Homework Statement I don't understand the derivation of the right side of the last equation. Homework EquationsThe Attempt at a Solution I got to this point, I also don't understand why it did not include C_2 for the variation of temp. along the fin. I am guessing the right side is the...

Homework Statement Homework EquationsThe Attempt at a Solution I thought it would become d/dx(-kAc*dT/dx)+hp(T-T)=0 instead of where the equation in the red box? I don't see how are they equivalent [/B]

Hello all I have a practical question regarding heat transfer within my laptop. My laptop uses a shared-heatpipe design, meaning that my CPU and GPU are connected by a common piece of copper, and then each chip goes off to its own heatsink/fan. While playing games, I was monitoring the...

Homework Statement (a) What is the purpose of a silvered coating, usually of a good conductor, on the outside of most insulation? The Attempt at a Solution [/B] The silver coating on the outside of most industrial pipes and lagging (Insulation) is primarily to reduce the surface’s...

Homework Statement (a) Explain how heat is lost from a hot surface to the surrounding air. The Attempt at a Solution We will assume as there has been no other stipulation that the effect of radiation is negligible and thus we are taking purely about conduction. We will also assume as there...

Homework Statement An appropriate correlation for heat transfer by natural convection from a horizontal pipe to the atmosphere is Nu=0.53Gr^0.25 Pr^0.25 Where, Gr= (αp^2 d^3 (T_1-T_f )g)/μ^2 And Pr⁡〖= (C_p μ)/k〗 Show the above correlation can be simplified to h...

Homework Statement A furnace wall consists of three layers of material as shown below. The thermal conductivities are: Firebrick = 1.15 W m–1 K–1 Insulating brick = 0.17 W m–1 K–1 Ordinary brick = 0.62 W m–1 K–1 Calculate: (i) the thermal resistance of each layer (ii) the heat loss per...

Homework Statement A small reheating furnace wall consists of 200 mm of firebrick. The inner surface of the wall is at a temperature of 320 °C and the outside temperature is 35 °C. Calculate the rate at which heat is transferred, by conduction, through unit area of the wall. The thermal...

Homework Statement A cylinder is fitted with a piston and is in thermal contact with a heat bath at 273K. Initially the volume in the cylinder is filled with 10kg of pure H2O and about half of this is liquid and the other half is solid. The piston is lowered so as to reduce the volume by 2 ×...

<< Mentor Note -- poster reminded to use the standard Template >> Question Three A pipe of outside diameter 200 mm is lagged with an insulating material of thermal conductivity 0.06 W m-1 K-1 and thickness 75 mm. The pipe carries a process fluid at a temperature of 300 °C and the average...

Question: A pipe of outside diameter 200 mm is lagged with an insulating material of thermal conductivity 0.06 W m–1 K–1 and thickness 75 mm. The pipe carries a process fluid at a temperature of 300 °C and the average temperature of the outer surface of the lagging is 45 °C. (a) Estimate the...

Hi guys, I am newbie on thread and currently working on a project I need some help on the Heat flow on multiple walls. Here is the setup (see figure below) The first wall is a Steel material which has a 350C temperature(1kwatts) and the an Air Gap is present then followed by a Plastic wall...

Homework Statement I'm a little bit stuck with this exercise.A small body with temperature T and emissivity ε is placed in a large evacuated cavity with interior walls kept at temperature Tw. When Tw-T is small, show that the rate of heat transfer by radiation is $$...

Homework Statement A 0.25 kg piece of ice at -30 C is warmed by an electric heater and the following graph of temperature is produced. Assume that there has been no loss of energy to the surroundings. - Use the info on the graph to determine the power output of the heater - Explain how long...

I have a long steel uninsulated cylinder filled with hydraulic fluid (let's say it's mineral oil), and I need to figure out how many barrel heaters to clamp onto it in the winter months to prevent the steel surface temperature from dropping under 40 degrees Fahrenheit. My question is, how do I...

Hello Physics Forum Users! I have an annoying situation with the Finite Heat Release Equation used to simulate combustion and expansion processes in an internal combustion engine. The equation is as follows: Nomenclature: P = Cylinder Pressure (kPa) θ = Crank Angle (Deg) k = Specific Heat...

Homework Statement I am working on a problem where I need to determine the time taken for an air heater with an 8kW output to heat a volume of air of 9m^3 by 25C. I am neglecting all losses at the moment. It almost seems too simple in my mind that I'm concerned I'm overlooking...

hi, I met a problem about heat transfer in cylinder, if you can help, I will appreciate it. The question is simple. I want to know the transient heat distribution in a cylinder with internal heating(constant temperature not constant flux). The boundary conditions comprises two constant...

I have a practical engineering problem for which I really have no background on how to solve. I am looking for help, but don't even know what field of engineering would be likely to know the answer, so not quite sure where to ask. Any formulas that I might use to calculate the answer would...

Hi, wondered if anyone can give me a pointer on this problem I am working on. 6 Diesel engines each with power 55kW running, given output cooling water temperature of 80°C, and required return temp of 60°C. The coolant is to be fed through a heat exchanger, with the heat exchanger outlet to be...

Homework Statement A fuel gas consists of 75% butane (C4H10), 10% propane (C3H8) and 15% butene (C4H8) by volume.It is to be fed to the combustion chamber in 10% excess air at 25oC, where it is completely burnt to carbon dioxide and water. The flue gases produced are to be used to generate 5...

The Nusselt number represents the ratio of heat transfer by convection relative to conduction. At the onset of convection does this correspond to a Nusselt number of 1?

My colleague has been developing a hybrid water/forced air heat transfer system for a prototype lighting solution we are developing. I am struggling to get my head around the calculations required to figure out exactly how many watts of energy (heat in this case) are being transferred to the...

I would really like a logical explanation for some of the factors that affect convective heat transfer coefficient. I have only found mathematical one. For example: 1) Properties of the fluid: 1)Velocity: My professor said that the lower the velocity the more time the fluid gets to interact...

Homework Statement Homework Equations I'm not sure. The Attempt at a Solution I tried to solve this as you would with electric charges. I added up the temperatures and then divided by 2, to get (C) 17.5 degrees Celsius. The answer key gives the answer as (D) 20.0 degrees Celsius. I'm not...

Hello, I have studied about heat transfer through conduction only in steady state but I wondered about this problem that I created. Suppose you have a box that is insulated from all sides but Suppose a constant heat flow from that wall. Inside that box you have M kg of water at the same...

Hello, So I am assembling some testing equipment. I have an active circuit, microcontroller, and two battery packs inside a black polypropylene case (which is around 1 ft x 1 ft x 0.5 ft). I was performing a thermal analysis because I want to make sure the electronics do not heat up past around...

Hi I am trying to do a transient heat transfer calculation. The water flowing through the pipe is laminar (1 m/s, id = 0.0127 m, Re_d = 0.01) transferring heat to the pipe via convection, then the pipe (od = 0.015875 m, l = 144 m) transfers heat to the ground again via conduction. I found this...

I am trying to calculate how much a foil liner helps keep the inside of a package cool. I have calculated the rate of conduction but am now concerned with radiation. Above is the equation I am using. The emissivity for the material is 0.05, the area is 1 m^2, the outside air temp is 295...

Hi, I am looking to simulate a very - seemingly - simple case. Any advice on a software package would be helpful - preferably gui which doesn't have a steep learning curve. I want to model the heat flux into a sphere from the outside. The dimensions of the sphere are not important to me. I...

n the heat transfer analysis of boundary layer flow of viscoelastic fluids many researchers see the variation of temperature of fluid inside the boundary layer with Prandtl number, for which they use prandtl number 0.7, 2 , 3, 4 .. This is what generally the researchers do.. Currently i am...

Hello, I have a question for expert in termodynamics. Let's assume I have a copper conductor made of two big disks connected with a very thin wire. Let's imagine I have a current pulse starting somewhere in the wire, and assume the current density is high, like 100A/mm^2. This current will...

Ques: I would like to calculate the time taken where the internal pipe's temperature would reach 150 degree Celsius too. A heat source will be constantly feeding on outside pipe where the temperature will be maintaining at 150 degree Celsius. Feel free to make any assumptions if there is...