Heat transfer Definition and 875 Threads

Hi, I'll describe my problem more specific. I have a continuous flow of this polymer thread (polystyrene) at 465 °K (190°C sorry I'm metric) that needs cooling down. It passes trough a water bath which is kept at 310°K (35°C). Now i try to calculate the heat exchange into the water, to...

Hi all! I am trying to solve a system of partial differential equations in Matlab, with both derivatives in time and space domains. I am using the pdepe function for that. The system is, to be simple, a sort of solar thermal panel, made of three layers: an absorber plate, a fluid layer of...

Homework Statement Is my approach correct? Thanks all :) a)The specific heat capacity of water is 4200Jkg-1K-1 while the specific latent heat of steam is 2.26x106Jkg-1. Explain what is meant by the statement in italics. b) Explain, in terms of molecular motion, the large difference between...

Homework Statement Three building materials, plasterboard [k = 0.30 J/(s m Co)], brick [k = 0.60 J/(s m Co)], and wood [k = 0.10 J/(s m Co)], are sandwiched together (as I've tried to show below). The temperatures at the inside and outside surfaces are 28.9°C and 0°C, respectively. Each...

Homework Statement With the time rate of change for heat transfer: dQ/dt = kA(dT/dx) k = thermal conductivity constant A = boundary surface area dT/dx = temp gradient Homework Equations Can the solution for Q(t) be obtained from modifying Newtons Law of Cooling since dQ/dt is proportional to...

Homework Statement Consider a person in a room with an air temperature of 21C. The persons core body temperature is 37C and their surface tissue thickness is 5 mm. If the total surface area of their skin is 1.5 m2, and they are wearing clothes of a thickness of 2 mm and the surface heat...

When modelling the heat transfer through a plate using fouriers equation, what difference would it make if the width and length of the plate were set to a specified value rather than being infinite?

Homework Statement A circular floor 9.15 m in diameter has an emissivity of 0.8 and is at a temperature of 29.4C. The floor is enclosed by a hemispherical metal dome which has an emissivity of 0.1. If the net rate of heat transfer between the floor and the dome is 660 W, calculate the...

I am setting up a hydraulic system on a cable laying machine. We don't have much space for the tank, and I am thinking of constructing it on the "wall" og a big 1m^3 stainless steel sand holder. That would make the tank With 5 faces in open air, 1 face With sand on the opposite side. I am...

I am designing a flat plate heat exchanger for a project and I am not sure where to start with the hand calculations, specifically the LMTD and E-NTU methods, also how to work out the parameters which i will need to complete these methods such as area and number of plates. My deadline is soon...

Hi, I currently have a project running involving dynamic insulation. I am struggling to develop a 1D transient analytical model to compare to my experimental results. I have used the separation by variables method in the most basic form over 1 solid material but have failed to adapt this to 3...

I'm having a problem with understanding how energy flows from one body to the other. So gases at high pressure travel towards low pressured areas. So there is a reason behind this. Since molecules of gases have the tendency to move away from each other, they travel towards low pressured areas...

Water is being sprayed at a hot flowing material to cool it from 350F to 290F. Let's assume that steam is produced when the water hits the hot material. How would I set up the heat transfer equation to solve for the mass flow rate of water required to cool it from 350 to 290? Assumptions...

So a friend of mine is living in an apartment with central heating but the radiators are removed, so there are just the pipes. He seems to think that if you cut aluminium jar caps and cover the pipes with them, it will increase the surface area of the pipe and therefore heat the room more. The...

Hi! I am modelling heat transfer through the oxide scales on the surface of steel but I cannot find the accurate properties of oxide scales. I need thermal conductivity, density and specific heat capacity. They shloud be dependent on temperature. I have found only one book in which are some...

Hello, I have a swimming pool with a waterfall feature. I need to know how much does the waterfall contributes to cooling the pool. I tried to use Newton's law of cooling, but I have a problem with the Heat Transfer Coefficient in this case. Following are the Givens: Waterfall Width= 5m...

OK so I have a little issue I'm dealing with.. here are the basics.. There is a material that was filtered and came out of the filtration process at about 330 degrees (it comes out as a solid filter cake). It somehow caught on fire which caused the deluge system to activate. I just want to...

So the internal energy of a system changes if work or heat is transferred between itself and its environment. Say you compress a gas and therefore do work on it, increasing its internal energy. According to Newton's 3rd law, shouldn't the gas also do work on its surroundings. How come this isn't...

I'm going through the solution to a problem that was assigned to my class and there's a step I don't really understand which I think is a concept I'm misunderstanding. 1. Homework Statement The curved surface of a cylinder of radius R and length L is insulated. The face at x = L is maintained...

Aluminum foil reels have to be preheated for manufacturing but it's inefficient (the doors aren't sealed and the material isn't in close contact with heating elements at the sides). I'm considering an initiative of more efficient design. How difficult would it be to evaluate heat transfer if...

Hey, I have a question regarding heat transfer. I was wondering if a heat sink works in both ways equally effective. What I mean by that is if we submerge the fins of a heat sink into a hot environment, will it transfer the heat equally effective to cold environment which it's mounted on...

In terms of Heat equation it is d2T/dx2 + qgen = qstored assuming steady state, heat flows in one direction. But I have seen examples where energy is balanced in terms of qconv + qcond + qgen= qstored Why is the first equation just not the first derivative of Temperature with respected to x...

I am not familiar with non steady-state heat transfer problems, any resources on where I could get started would be a huge help: There is a pipe filled with a fuel/air mixture. This mixture is ignited at one end of the pipe, so that the flame front propagates through the pipe. How can we...

Homework Statement Steam in a piston-cylinder assembly undergoes a polytropic process. Kinetic and potential energy effects are negligible. For the process, determine the work and heat transfer, each in Btu per lb of steam. p1 = 100 lbf/in2 p2 = 40 lbf/in2 v1 = 4.934 ft3/lb v2 = 11.04 ft3/lb...

According to this article, it is beneficial to scale down heat exchangers due to the decreased distance the heat has to travel, and therefore the decreased thermal resistance and increased heat flow. "the best way to remove heat from a CPU is to minimize the distance heat must travel from a...

This question is easier to explain with an example. A silicon microprocessor consumes 100W of real power. If the surrounding air has a temperature of 22°C, and the temperature of the microprocessor must stay below 60°C, how much heat must the microprocessor dissipate? This isn’t a homework or...

Hi, I am working on constructing a thermal circuit where I am using the concept of natural convection from a vertical hot plate in the shape of a DVD. In order to calculate the Grashoff number, I have to use the characteristic length. What should I take as my characteristic length? The disc OD...

Not sure if I'm getting this right, my answer seems very small, can anyone advise? Question- butanol at a temperature of 28oC is pumped at a velocity of 14ms-1 through a 100mm diameter tube kept at a wall temp of 90oC. The properties of butanol are below. Determine the convective heat...

How do I find the heat transfer coefficient for a meteorite? The meteorite is made of carboneus chondrite, but approximations with heat transfer coefficients for regular stones or rocky materials would be just as fine. Furthermore, how would I calculate the energy required to vaporize 1 g of...

One quick question about heat transfer. during conduction heat transfer occur when molecules collide with each other .heat from one end of the object is transferred to other end .when molecules from end 1 collide with near by molecules of end 2 they transfer their energy to those nearby...

I am a little confused, because I know how refrigerators work with a refrigerant and a compressor and heat exchanges, and I am looking to build one myself, just wondering because I was looking for refrigerator compressors online to buy. Do they have an inlet for refrigerant or is the...

Hi, I'm new to this forum. A colleague and me have a discussion in heat transfer between to bodies (thermal contact conductance) Let's say yo have a body A and B (witch are identical), A is heated to a hundred degree Celsius, B is 0 degree Celsius. You then put the bodies A and B together. You...

Hi, I've recently been given a series of questions on heat transfer to do and have done most of them with general ease, but this one question I've been stuck on for ages and i can't seem to figure out: "A double pipe heat exchanger is made up from a length of 25mm i.d. steel pipe of 2.5mm...

Homework Statement A 6.00-kg piece of solid copper metal at an initial temperature T is placed with 2.00 kg of ice that is initially at -20.0C. The ice is in an insulated container of negligible mass and no heat is exchanged with the surroundings. After thermal equilibrium is reached, there is...

Homework Statement Two large plates are parallel and close to each other, vacuum is between them. they are held at 2000K and 3000K. What is the energy transfer rate between them. Homework Equations The energy emission rate per unit area-the Stefan-Boltzmann Law: $$R=\varepsilon\sigma T^4$$...

Homework Statement Dry saturated steam at a temperature of 180oC is to be produced in a fire tube boiler from the cooling of 50 000 kg h–1 of flue gases from a pressurised combustion process. The gases enter the tubes of the boiler at 1600oC and leave at 200oC. The feed water is externally...

Hi all, I have a unique problem that I need help with A company's curing oven's exposed surface temperature is measured at 80°c when the surrounding air is 23°c. You think it should be insulated and wager to pay for the cost of this yourself if you can keep the savings incurred. Is this a smart...

If I know the temperatures of the two thermal reservoirs (one hot, one cold), the area of contact between each reservoir and the body, and the coefficients of conduction, it seems like I should be able to calculate the equilibrium temperature of the body, but I can't seem to figure out how.

I need create a math model to predict the temperature of a copper pipe with hot air flowing through based on the temperature of the air, properties of the air and copper, and the surface area of contact between the air and the pipe. The pipe will start cold but I will be looking to the...

Studying for a test, and this problem stumped me because of the confusing nature of the question... Not sure where radiation shld come into play. Any help appreciated! THANKS! 1. Homework Statement The walls of an apartment are made of two layers of mat with a heater layer in between...

Homework Statement A copper tube has a 2 cm inside diameter and a wall thickness of 1.5 mm. Over the tube is an aluminum sleeve of 1.5 mm thickness having 100 pin fins per centimeter length. The pin fins are 1.5 mm in diameter and are 4 cm long. The fluid inside the tube is at 100 ºC, and the...

what is Stanton Number? and its use/application in convection heat transfer coefficient?

1) PROBLEM: Task is to find the thermal conductivity of steel experimentally. I have conducted relevant experiments and I am trying to solve for the thermal conductivity (k) itself. My final however is ten times too large in size, and I am having trouble identifying where the error is coming...

Hi am a bit stuck on understanding how these two correlations can be similar I am wondering if anyone can ahead any light Can anyone solve Correlation for heat transfer by natural convection from a horizontal pipe to atmosphere is; Nu = 0.53Gr^0.25Pr^0.25 Nu = hd / k Where, Gr =...

Right, I'm sure this is bread and butter to a lot of you but I have just been introduced to the SFEE. mgz+0.5mC^2+H +Q = mgz + 0.5mC^2 +H+W Where Q is the heat transfer, W is work done and H is enthalpy. Where is it assumed that the heat energy is in the energy balance? If heat is added where...

Hi friends, i have developed an code for a non linear heat conduction in 2 dimensions with dirichlet boundary condition by finite difference method in Matlab. my code is running slow to give output. If anybody has any idea of solving this equation or have written any Code for this equation...

Could someone explain what an object's soak back temperature would be? My idea of what it is relates to an object's temperature peaking before cooling down due to the absorption of leftover energy (i.e. a car engine is being cooled by a fan. The fan and engine both shut off, and the engine...

Hello, I am trying to calculate the thermal radiation heat transfer to a shipping container which would be painted white. The purpose is to size an air conditioner for equipment, not living conditions. I have already calculated heat from the other sources. The desired internal temperature is...

I'm working on a problem involving steel structural members on the exterior of a building. I need to figure out how much insulation (for summer conditions) and possible heat tracing (for winter conditions) would be required to maintain minimum and maximum temperatures. I know I need to use the...

Hi, I was provided a http://eng-tips.com/viewthread.cfm?qid=372664# that I'm lost on. I was given an equation that we solved for earlier in the semester using the finite difference (dx method). (first image below). The http://eng-tips.com/viewthread.cfm?qid=372664# wasn't clear when...