Heat transfer Definition and 875 Threads

Homework Statement A composite pipe made of steel pipe ( ks = 16 W/m.K) of inner and outer radius of 0.5 and 1.0 cm and a plastic pipe (kp = 0.092 W/m.K) of inner and outer radius of 1 and 1.25 cm, respectively. If the inner surface of the steel is maintained at 900 °C and outer surface of...

Looking back to heat transfer by convection, which means denser molecules move down, lighter molecules move up. And then water at 4°C expands when cooled further, and at 0°C it contracts when heated. So if water at 0°C in a container is heated from the bottom, its molecules should...

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 bar steam from water...

Hello everyone, I was hoping to get some insight on a model I am trying to create. Quick background in case it is important, I am now working at a new internship I landed for the summer doing some modeling and what not on areas of physics I have never worked on before. It has also been a few...

A bar of iron is 0.5m long, 0.2m wide and 0.1m high (which means its volume is 1.0 × 10−2m3 and its surface area is 3.4 × 10−1m2 ). Iron has a density of 7900 kg m3 , a heat capacity of 400 J kg◦C , and a coefficient of linear expansion of 1.2 × 10−5 . The bar of iron is initially at 600K...

I'm considering making a plastic melter / extruder for making my own 3D printer filament as opposed to buying the spools of it. The basics of the project are simple, but the hard part (for me at least) is making a heating element that has a control on it so that I can turn the heat up or down...

Homework Statement A satellite to reflect radar is a 3.5-m-diameter, 2.0-mm-thick spherical copper shell. While orbiting the earth, the satellite absorbs sunlight and is warmed to 50 °C. When it passes into the Earth's shadow, the satellite radiates energy to deep space. You can assume a...

How to calculate cooling time for a aluminum block in a steel crate placed in a room...both at 90°c ...how much time aluminum block will tak take to cool down to 25°c?

I want to pursue EE, but there are still some subjects in ME that I enjoy. Do heat transfer topics ever come up in EE? I would imagine cooling circuit board requires lots of knowledge of heat transfer/thermodynamics. I studied Haberman's PDEs as part of my chemistry undergrad and all it talked...

If i have atm temperature around 32 deg Celsius, volumetric flow 6000m3/h, fluid temperature inlet 47 deg Celcius. How to get minimum possible dimension for my canal if its maximum possible length is 180 m and fluid temperature outlet at least 40 deg Celcius?

Hi all, I am currently considering a heat transfer problem. In this problem a rectangular vessel made of stainless steel is heated by a surrounding jacket with hot combustion flue gases flowing through it. This means that the heating of the rectangular vessel is achieved primarily through...

Homework Statement have you ever encountered this equation? it is the energy differential equation through a rectangular tube Homework Equations uρ(∂i/∂x)+vρ(∂i/∂y)+wρ(∂i/∂x)-[∂/∂x(k∂t/∂x)+∂/∂y(k∂t/∂y)+∂/∂z(k∂t/∂x)]=0 heat transfer coeff is k The Attempt at a Solution have you any idea how to...

Homework Statement Homework Equations P = k A \frac{dT}{dx} The Attempt at a Solution a) Assuming steady state transfer, energy transfers through rods at the same rate everywhere. Letting T be the temperature at the point of welding. P_1 = k_1 A \frac{T_h-T}{L} \\ P_2 = k_2 A \frac{T -...

Homework Statement Liquid ammonia is heated as it flows at a mean velocity of 2 m s–1 through a circular pipe. The pipe, which has an internal diameter of 75 mm, is at a uniform temperature of 27°C, and the ammonia at a section 1.2 m from the inlet to the pipe has a temperature of –23°C. Use...

Homework Statement Homework Equations The Attempt at a Solution This is a solved question. The answer is given above. I can't understand why h1=h2. [/B]

I'm trying to design a double pipe heat exchanger for two different water lines. One line is chilled water of approximately 7degC and the other is chilled water return from an air handling unit, of around 12degC. I want to design this heat exchange for a capacity of approximately 22kW. The part...

Hello Physics Forums! My problem is as follows. I have a device that produces heat via Nichrome coils. I want to heat another small piece of metal (in this case stainless steel) with those Nichrome coils. I need to reach 175 degrees C, and so far I haven't found a readily available thermal...

Homework Statement Its been assumed that the surfaces TL and TR of the same constant temperature. Homework Equations Tmax = TL/R + (qdoto*L2)/(8*k) q = ΔT/R Rconvection = 1/hA The Attempt at a Solution The problem I am having with this question is conceptualising which dimensions to use...

Hi there, I have a problem that I cannot find a solution too. In this problem I have a fuel (approximately natural gas) supply which is combusted when mixed with air inside a burner. The flame that is then generated is used to heat up a sealed cylindrical vessel (the flame is on the outside of...

Hi I am planning on building an immersion heater to heat oil when it is -20 C degrees outside. I need some help calculating the heat transfer. I want to find out how long it would take to heat around 10 litres of oil from -20 degrees to 10 degrees using an immersion heater with a constant...

Homework Statement A furnace is constructed with 0.5 m of fire brick, 0.15 m of insulating brick and 0.25 m of ordinary building brick. The inside surface-temperature is 1530K and the outside surface temperature is 525K. The thermal conductivities of the fire, insulating and building bricks are...

Hello guys, in the question attached, my understanding is that there is a heat transfer that heats the fluid from an initial at the input, to at the output. This heat transfer is via convection from walls of temperature . Firstly, . Because the walls are and the fluid is of a lower...

1. Question 2. The attempt at a solution Now I'm not sure where to go next? Do I work out the local heat transfer coefficient at 1.2m or just the heat transfer coefficient? Using h = Nu × k/x or h = Nu × k/d Thanks, Sam.

Homework Statement Homework Equations I could really use a push on how to approach this problem. My primary problem is it asks for the heat flux into the page, which makes no sense to me as that is the z direction and this is in the x/y plane. If anyone could explain this problem and maybe...

water is flowing in the closed looped pipe equipped with preheater. there are pressure and temperature gauges before the preheater and after the preheater. which pressure gauge should i use to know whether the outlet preheater temperature has reached the saturation temperature?

Homework Statement A sphere of radius r_s is at the center of a spherical shell of inner radius r_i=10\, r_s and thickness s = 10\, {\rm cm}\ll r_i. The sphere has a temperature T_s=1073\, {\rm K} and and an emissivity e=0.90. The inner surface of the shell has a temperature T_i = 873...

Homework Statement "In a container of negligible mass, equal amounts (in weight) of ice at 0◦C and steam at 100◦C are mixed at the atmospheric pressure. Assuming no heat exchange with the surroundings, what is the temperature when the system reaches equilibrium? What are the fractions of...

Homework Statement An infinitely long cylindrical shell has an inner radius a and outer radius b. If the inside is maintained at a temperature Ta and the outside at a temperature Tb, determine the rate of heat flow per unit length between inner and outer surfaces assuming the shell has a...

Homework Statement If 5% of the heat available for steam production is lost to the atmosphere, determine the amount of steam raised per hour when the total flow of flue gases is 1400 kmol h-1. qmH = 1400 kmol h-1 Flue gas temperatures: Inlet = 1832°C Outlet = 300°C Water temperature: Inlet...

Hello everyone. I've been doing a bit of independent study for this topic without much background and so my thermodynamic knowledge is fairly limited. I came across this problem and I'd like some assistance with it! If anyone can help out, I would be very grateful. A lot of the equations came...

Homework Statement : [/B]At the beginning of the compression stroke of a two-cylinder internal combustion engine the air is at a pressure of 101.325 kPa. Compression redeuces the volume to 1/5 of its original volume, and the law of compression is given by PV^1.2 = const. If the bore and stroke...

Hello all, this is related to a project that I am working on. It is not directly related to the project but as part of it, I thought it would be a good idea to check the temperature difference that I need to maintain in order to effectively transfer a certain amount of heat between the TH in a...

What is the physics behind heat transfer between two panes of glass? Commonly windows now are filled with argon (some cost) or krypton (pricey) At a given temperature all gas molecules have the same energy per mode, so heavy ideal gas molecules move more slowly than light ones, so heat...

I am a little unsure how to get started with a homework question. Essentially, I have to calculate the local heat flux at a distance 1.2m (x) along a pipe. I have the fluid's properties and have calculated the Reynolds number, for which I've determined the flow to be turbulent and therefore do...

Hello, Im having some issues with my task. 1. Homework Statement The heat generation rate of a cylindrical fuel (D=0.2 m and 1 m long) is 160 kW. The thermal conductivity of the fuel is 100 W/mK and its surface temperature is maintained at 283 K. Determine the temperature at the axis...

Hello All, I have a question for heat exchange calculation and hope someone can help. I would like to recover the "cooling energy" from a ice melting pool for air-conditioning for a small office. I plan to install three fan coil units with 800CFM for the office with closed loop water pipe to...

I have a cuboid shaped box. It is being used as a chilling tank in my refrigeration system based on Evan Perkins cycle. For heat load calculation I tried to calculate the heat leakage in the sysyem. So I considered conduction and natural convection. I am in preliminary stage, so no use of...

I left my unopened icy cold Coke out on my desk yesterday. When I came in today it had, of course, lost it's icy edge and had achieved room temperature. Then I asked myself...will my drink ever actually achieve room temperature or will it always be slightly colder then room temperature? Can...

Homework Statement Can you please help me with this thermodynamic question?I am not a student. An aluminum cylinder with an interior area of 4.1875 sq ft (or 603 sq in) contains 7.445 lbs of CO2 gas under pressure.The volume of the cylinder is .582 cu ft.The temperature of this gas is 110 deg...

When calculating heat transfer, how would one know when to use Q=T*m*(delta s) versus Q=m*(delta h). I'm confused when we should calculate using entropy versus enthalpy. Anything helps. Thank you!

I’m working on an experiment and would appreciate some guidance to characterize the performance of it. I have a small homemade copper coil submerged in a 3 gallon water tank. I’m delivering hot water to the coil that in turn heats the water in the tank. I sense I’m looking for a rate of heat...

Homework Statement I do not need to solve this problem, see below. EXAMPLE 7.1 Air at a pressure of 6kN/m2 and a temperature of 300C flows with a velocity of 10m/s over a flat plate 0.5m long. Estimate the cooling rate per unit width of the plate needed to maintain it at a surface temperature of...

Just Qualitative Analysis: There are many ways of cooling a coffee cup. But here I want to understand about concept of fins. So I am using a spoon to enhance the heat transfer rate. Put the spoon vertically in the cup. We have two ways to put the spoon, other one is upside down. I am curious to...

Homework Statement a copper pot's radius is 12 cm, the thickness is 5 mm. It is placed on the stove for boiling, if the temperature of the stove is 115 oC while the water is 100 oC. How much of water that evaporates per minute Homework Equations ΔQ/Δt = (A)(k)(ΔT) / (L) Q=mcΔT The Attempt...

Homework Statement [/B] We are heating a semi-infinite slab with a laser (radius of a stream is ##a##), which presents us with a steady surface heating (at ##z=0##), everywhere else on the surface the slab is isolated. How does the temperature change with time? Look at the limit cases: at ##t...

Homework Statement Would really appreciate if you could lend me a hand with this tube and shell exercise.[/B] m=0.24kg/s ##D=2.5*10-2m## ρ=850 kg/m^3 cp=2000 J/kg*K μ=2*10-4 kg/m*s λ=0.3W/m*k Homework Equations Dittus-Boelter:Nu=0.023*Re0.8*Prn where n=0.4 heating and n=0.3 for cooling, so in...

Homework Statement I have a confusion regarding areas. Usually in fluid flow I am using the A=(pi*D^2)/4 However in heat transfer we usually use A=pi*D*L Could you please explain this?I mean in first case(fluid flow) it is cross sectional area and in the 2nd case(heat transfer) is like the...

Homework Statement I would really appreciate if you could give me some hints regarding what exactly to do at iv)[/B] iv) Given formulas: Homework Equations f(y)=(ro*R^5/E*t^2) The Attempt at a Solution we know that f(y)=0.75 1ton TNT=4.184*10^9 J ro=1.003kg/m^3 We have the above...

Homework Statement Homework Equations The Attempt at a Solution I do not know exactly how to start this problem. I would really appreciate it if you could give me some hints. I know that e^ - t/tau=T(t)-Twall/Ti-Twall where tau=m*cp/hA where h=convective heat tr.coeff and T(t) is desired temp...

Hi Guys While studying physics for my masters (doing it in material science engineering), huge amount of questions appeared. First, let's imagine two experiments 1) One enclosure with perfect reflective walls (R=1 over the entire thermal radiation spectra) at a temperature T1 and a body inside...