Heat transfer Definition and 947 Threads

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 I have to come up with a program that calculates the nodal temperatures of a sheet with a slot with 2D conduction. Due to symmetry the shape can be reduced to an L shape. Matlab and loops have always given me trouble, so I tried the Interactive Heat Transfer 4.0...

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...

Homework Statement It is well known that wind makes the cold air feel much colder as a result of the windchill effect that is due to the increase in heat transfer coefficient with increasing air velocity. The windchill effect is usually expressed in terms of the windchill factor, which is the...

I must be doing something wrong here but I cannot figure out what it is1. Homework Statement An insulated beaker with negligible mass contains a mass of 0.350kg of water at a temperature of 70.1∘C. How many kilograms of ice at a temperature of − 11.6∘C must be dropped in the water to make the...

I've been getting mixed views on how to identify fins in different situations. From my class I know that fins have a lot of convection around them, and the fin material in itself has high thermal conductivity, so there is negligible temperature gradient along its breadth. However today we...

How can we calculate the overall heat transfer coefficient experimentally for a system?

Hey guys, I was trying to find the answer to this question but could not seem to find anything. I am trying to figure out how to calculate heat transfer rate between a liquid and a gas. Say the the liquid is water in a chamber (with no heat transfer to the walls). The gas is the residual...

Homework Statement I have attached the problem as an image and they are same as below. The collector-receiver combination tested above is chosen for use in a solar thermal power plant. plant consists of 100 rows of collector-receiver modules. For the receiver efficiency use the value...

Hi, I am trying to create an apparatus to measure the thermal conductivity of woody pellet based on peltier effect. the fundamental equation for thermal conductivity is Q"=kA(Δt/Δl), where k is thermal conductivity. A is the area of pellet, Δt is measured by using thermocouple and peltier...

Homework Statement A piston/Cylinder arrangement of initial volume 0.025 m3 contains saturated water vapor at 180 degree Celsius. The steam now expand in a Polytropic process with exponent n=1 to a final pressure of 200 kpa while it does work against the piston. Determine the heat transfer...

I'm looking at the dynamic state of heat transfer through a concrete slab. Suppose heat is turned on at t=0 and the coils/tubing are 6 inches below the surface. Is there a formula or way of calculating the temperature at the surface at time = t? I found a formula for thermal lag on wikipedia...

Homework Statement 4 rectangular long fins are assembled on a 40x40x6 mm aluminum heat sink with the fins being 30 mm long, t=4 mm in thickness and 40 mm wide. The system generates 3 W and the room temp is maintained at 20 c. What is the temperature of the substrate surface that holds the...

In the case of reversible heat exchange which the cooler body rises in temperature from T1 to T2, it requires that the temperature difference between the system and the heat source must be infinitesimal in every step. Usually the model is like that: Give a heat reservoir of temperature slightly...

hi, I am running some scientific experiments, and I need a sheet of materials that is extremely good conductor of heat in z axis (through its thickness), I mean it is a good longitudinal heat conductor. I have been doing some researches and some people told me Ni and Mo foils are good at 90...

Homework Statement The cross section of a wall is shown in the figure below. To reduce the heat flow, an air gap (still air) of 6cm is created between the brick wall layers of 14cm thick, each. The thermal conductivities of the brick wall and the still air are: Kair = 0.032 W/m.K and Kbrick =...

Homework Statement Hi all, I am helping in designing a conveyor that takes freshly milled mild steel bars and submerges them in a tank of cooled water to reduce their temperature enough to to not damage the proceeding equipment. The tank of water will be connected to a separate...

Afternoon all, I am interested to hear any and all suggestions as to how one would go about modelling the rise in temperature on the "safe" side of a wall, after a given time period over which the other side was exposed to a hydrocarbon pool fire. The configuration I have been looking at...

I have tested two radiators with 90 degrees celcius of hot water going through it. The radiators were placed in a wind tunnel with the ability to control air speed. The bigger radiator cools the water more than the smaller radiator and the air temperature rise after the air has gone through...

Heat transfer -- aeroheating and material thickness I'm trying to size the thickness of a shroud to encapsulate a payload on a small rocket. We're using carbon fiber pre-preg (k=6.83 W/m-K) and (per the aeroheating analysis based on the trajectory) the max heat rate is 908 kW/m^2. The...

Hello, In heat transfer, for the components to be in parallel, does that simply mean that the heat is transferring through all of the components at the same time, such that ΔT is the same for both, similar to how the voltage is the same for two components in parallel of a circuit?

Homework Statement Two bodies of masses m_{1} and m_{2} and specific heat capacities s_{1} and s_{2} , are connected by a rod of length l and cross-sectional area A, thermal conductivity K and negligible heat capacity. The whole system is thermally insulated. At time t=0, the...

Hi There, I came across the following passage in Sam Glasstone's 'Nuclear Reactor Engineering' See where I underlined in red that taylor series expansion? I don't understand how (dt/dx)_(x+dx) is equal to that. I know it's a Taylor series expansion, but where did the x+dx go?

I am wondering if there is any way or formula to find Heat transfer from a fix volume of gas that is release into a sealed room. Eg. 1m^3 of 37 degree gas is released into a 100m^3 room which has a temperature of 28 degree. What is the heat transfer from the released gas?

Homework Statement The underside of a smoky layer 7m x 10m is radiating like a flat, isotropic plate at 440°C to the floor of a compartment 1.85m below. The mean emissivity is 0.45 and the floor is homogenous/flat plate at 40°C. What is the rate of heat transfer from the smoky layer to the...

I had a quick thermal dynamics question... I'm looking into geothermal systems and I was wondering how to calculate the transfer from the ground, through a copper pipe into water. I know how to calculate the heat transfer from air of different temperatures though a medium, but I do not know how...

hi to everybody out there, entropy as i know of now is associated with heat which is basically energy in transit(for a rev. process it is indicative of unavailable part of energy) having said that what is meant by entropy change for a system as heat flows into or out of it(for instance consider...

I’m trying to understand the difference between how two styrofoam boxes of water cool when placed in a freezer. see attachment for picture Both boxes are 6’’ wide, 10’’ long and 6’’ high. Both boxes have an internal cavity of 4x8x4 (1 inch of insulation on all 6 sides) Box 2 has an...

Homework Statement An oak slab (ρ=545 kg/m3, k=0.17 W/(m-K), and c=2385 J/(kg-K)) of thickness 10 cm is exposed on one side to irradiation (1x10^5 W/m2) from a laser, which starts heating it up. Convection is negligible (i.e., h is small). The slab is initially at 23°C. (a) If the oak surface...

Hi Guys, this is my first post and I'd love a bit of help here, appreciated this may seem basic but it's been a few years since I did this last. I have water in a stainless steel pipe (ID = 0.0381m, OD = 0.0411m) network of roughly 10m length, at 120 bar, roughly 50°C (+ or - 5). This water...

I'm trying to evaluate floor heating systems for installation in my new studio, and I have to admit that my thermodynamics is a bit rusty... But I came across the following, and I could use a sanity-check. Basically, it's an in-slab heating element that claims to be 2.5x "more efficient"...

Hello fellow scientists, I'm working on describing the heat that's being stored in a sanitation pipe when hot water starts flowing through the pipe. I'm starting off with a simplified approach by assuming that the water in the pipe suddenly changes from 20°C to 60°C. I found a good start by...

1. Homework Statement and the attempt at the solution Alright, here is a picture of the problem along with my solution: My solutions gives the correct answer but the only part I don't understand is why the heat transfer coefficients are the same. If the two rods are made of different...