Heat transfer Definition and 875 Threads

I want to build a box that is warmed by sunlight. I was told that aluminum in the sun is much cooler than bare aluminum, both because it absorbs less light (even infrared?) and because it is a better black body radiator than bare aluminum. Is this correct? Ideally the surface toward the...

Homework Statement Sketched below is a solid, truncated cone, with a side profile of y=Cx. Based on the geometry, the area (in m2) of the left (truncated, x = 1m) and the right face of the cone is 4∏ and 36∏, respectively. The temperature of the left face is T1=50°C and T2=30°C. Assuming...

Hello everyone, I have this setady state, heat transfer problem; I hope you can help me with it. I have flux source of 400 W/m² (a lamp), and i want to calculate the heat flux passing through a surface arbitrarily placed and oriented in the space. There is air in between. How can i do this...

Homework Statement Hi guys, I don't really need help with answering the dollowing question but just have a quick question about it. I solved the first part of the question with an energy balance by letting q_{conduction} = q_{convection} to get the temperature of he outer...

Dear all, I am a bit stuck trying to find out how heat is transferred through an evaporator in a refrigerator. I was using Newton's law of cooling before I realized there are more complexities in the equation as the refrigerant is in a mixture of saturated liquid and saturated gas in the...

I am not really a heat transfer guy so I hope someone here can help me out here. I would like to know the formula to get this. Here is what I ma facing: I have a mandrel (basically a piece of cylindrical H-11 steel). It has OD of 3.5 inches and 37” in length. It has a core hole of about...

Hey all, I'm trying to simulate a simple chip-heatsink situation in SolidWorks using their thermal modeling suite. I have found an ideal set of parametric values for the chip to work at a reasonable temperature, but I need to figure out what the convection coefficient means in terms of air flow...

Hi There Does anyone out there know a good estimate or any real values for the total heat transfer area for the hot and cold sides of a domestic refrigeration system? i.e. the sum of the areas of the evaporator and the condenser. For the Evaporator: QL=UL.AL.(TL-T1) AL=heat transfer...

I am setting up a system where a rectangular plate is heated by a set of heater cartridges, producing about 4000 watts. This plate is in free convection air. It is used to melt plastic at regular invervals. I am trying to model the system so we can estimate temperatures of the plate to...

Homework Statement a) Liquid is stirred at constant volume inside a container with adiabatic walls. The liquid and container are regarded as the system. Is heat being transferred to the system? Is work being done on the system? b) Water inside a rigid cylindrical insulated tank is set into...

I have been tasked with calculating the cooling time of an extrduded steel rope running thru a water trough at a certain feet per minute speed. I've been researching conduction heat transfer equations and can't seem to find what I am looking for. I was oping someone could help me with the...

The heat transfer equation is Rate = k•A•(T1 - T2)/d where k is the heat transfer coefficient of the material. But I'm feeling that the other material transferring the heat should be important too. I mean if I were to touch Styrofoam at 50 degrees and metal at 50 degrees, the metal feels...

Hi people, I'm currently working on a project regarding entropy generation by (emissive only) radiative heat transfer from heat sinks. But I'm unable to find a proper treatment regarding Second Law analysis for Radiative Heat Transfer. Can someone give me the link to any book or any article...

Homework Statement Calculate the surface temperature of a stainless steel junction box that is in a 35C ambient temperature environment. There are electrical "boxes" that generate 30W of heat inside of this box. Homework Equations (1) Q_dot_total = Q_dot_conv + Q_dot_rad (2) Q_dot_conv...

Hi all, Doing some calculations on an air-cooled heat exchanger at the moment and could use some help understanding the variation of air-side heat transfer coefficient (htc) with flow rate. It's more of an intuitive problem really as I'm okay with the math, etc. So I know that as you...

I am currently in the process of designing a section of pipe in which a fluid will flow within, and would like to determine the specific heat transfer which may occur once the fluid enters the pipe, until it exits. The fluid will be flowing at a constant velocity "V" at a Temperature "T1" at...

ansys -- heat transfer within pipes and with surroundings hello , am doing my master in architecture n currently in my thesis stage and the thesis is about heat transfer within pipes and their influence on the surrounding atmosphere. i wish to know which is the right kind of analysis in...

what is the max free air heat transfer coefficient(film coefficient)? at 1000 c? i have a object that is at 1000 degree c by applying 900watt. i model it solid edge and apply heat generation load of 900 watt, from what i research air convection is 5-25 w/m^2/k. but when i apply that in the...

let say a cylinder(steel) is 6 cm diameter and length of 3.5 cm length. and is heated to 1000 degree c. in a room of free air and room temperature of 20. will convective heat transfer dominate? it radiation is negligible? what would the convective heat transfer be? what power(watt)...

whats would be typical value for free air convection heat transfer coefficient at high temperature of 1000 degree c? let say i have a vertical cylinder of diameter 5 cm and 3 cm high. and i heat it to 1000 degree c. the room temperature is 20c . what would the convection heat transfer...

Homework Statement Problem is in attachment pic. Homework Equations The Attempt at a Solution My attempt is on the pics 1 and 2. Firstly, is it valid to assume length as 0.075m? - For part (i), from the question it infers that one of the cylinders is applicable to the lumped...

Homework Statement A 2kW immersion heater for heating water in a large tank is to be made from a straight horizontal sheathed element of diameter 10mm. A sheathed element is an electrical resistance wire embedded in magnesium oxide powder and enclosed in a stainless steel tube, (there will...

I've got a problem with calculating (estimating) how much heat is flowing out of a metal bar in the following system; it seems like it should be simple but I can't see where to go with it. System: A small metal bar with length l=2.5mm, width w=0.2mm, thickness t=0.2μm with resistance R is on...

Homework Statement A steel cylinder of diameter 8cm and length 12cm is initially at 600°C. It is placed in oil at 20°C for rapid cooling, for case hardening of the surface layer. The value of h is 60W/m2 K. Use the numerical method. a. Determine the time in which the maximum internal...

How can I determine the thermal conductivity of two different aerial coolers' tubes, taking into account the ambient temperature of the air? The overall goal is to determine which cooler is able to cool water the best, but the data was taken during different outside air temperatures. Below...

Hello Gentlemen, Long time reader first time poster. I have a problem that I am trying to solve below. Problem 1 A metal copper rod say 20mm diameter has a constant heat applied to it of 150°C on one end. Ambient temp of Air is 25°C. What length rod do I need so the other end is...

Heat Transfer Qts Engine oil at 60 oC flows over flat plate whose temperature is at 20 oC with a velocity of 2 m s-1. The length of the plate is 5m. What is the film temperature and the rate of heat transfer per unit width of the entire plate? Additional information (at the film temperature)...

Heat Transfer Qts Engine oil at 60 oC flows over flat plate whose temperature is at 20 oC with a velocity of 2 m s-1. The length of the plate is 5m. What is the film temperature and the rate of heat transfer per unit width of the entire plate? Additional information (at the film temperature)...

Heat Transfer Qts Engine oil at 60 oC flows over flat plate whose temperature is at 20 oC with a velocity of 2 m s-1. The length of the plate is 5m. What is the film temperature and the rate of heat transfer per unit width of the entire plate? Additional information (at the film temperature)...

Engine oil at 60 oC flows over flat plate whose temperature is at 20 oC with a velocity of 2 m s-1. The length of the plate is 5m. What is the film temperature and the rate of heat transfer per unit width of the entire plate? Additional information (at the film temperature): Thermal...

Homework Statement A power plant generates 1300MW and operates at 315 °C a 20°C heat sink is available. what is the minimum rate at which heat must be discarded? Homework Equations not really sure how to begin this one, have a feeling it is related to dq=Tds at constant pressure giving...

A perfect gas is compressed in a cylinder reversibly according to the law pV1.3 = C. The initial condition of the gas is 1.05 bar, 0.34 m3 and 17 oC. If the final pressure is 6.32 bar; and given that cv = 0.7175 kJkg-1 and R = 0.287 kJkg-1. Calculate the following. (a) The work...

Homework Statement A straight, rectangular fin made from 2024 aluminium has a thickness of t = 3mm and length L = 20mm. Base temperature is 100 °C and it is exposed to a fluid at 20 °C. h = 60 W/m^2-K k = 185 W/m-K (a) Determine the heat transfer rate from the fin to the fluid per unit...

let say i have a piece of metal cylinder (say 3cm dia) and heat it to 500 c, and put it inside a hollow cylinder with inside diameter 3cm (so they are touching) and outside diameter of say 8 cm), the hollow cylinder is empty inside so water pass through. is there anyway to calculate the heat...

Q2​A large wall of thickness 5cm and thermal conductivity k = 0.65W/mK has a front surface with an emissivity of 0.8. At this surface there is radiation exchange with the surroundings and convection heat transfer to the air. The air and surroundings are at 22˚C, and the convection heat transfer...

Noobie question... Where there is Heat there is movement, so does that mean that whenever heat is present matter cannot be solid?

There is a course at my school called nuclear power engineering. It's an optional course, but it sounds important for a nuc engineer. The course has two prerequisite courses: fluid mech, and heat transfer which i can take as electives. The thing is that I didn't take statics or dynamics (not...

Hi, I need help tackling this problem and I wanted help since I feel lost. I have a probe running through a belt-furnace that has multiple stages for heating, I know the temperature of the oven at any given time (in minutes), the oven takes 8 hours and the Temperature profile looks like this...

Homework Statement A counterflow, concentric tube heat exchanger is used to cool the lubricating oil for large industrial gas turbine engine. The flow rate of cooling water through the inner tube (Di = 25 mm) is 0.2 kg/s, while the flow rate of oil through the outer annulus (Do = 45 mm) is...

I have three temperatures (temperature of the fluid going in, temperature going out, and the temperature of the surface of the tube). What I'm trying to figure out is the film temperature at which I should evaluate the flow properties. The film temperature is defined as T,f = (T,s +...

Hello everyone, For the purpose of my study I would like to know the relation between Pressure and Convection Heat Transfer. Especially the rough pressure when the convection becomes less significant. I did not find satisfying results on the forum. I have to study the global heat transfer...

Homework Statement A styrofoam cooler is in the shape of a rectangular box. Its interior dimensions are 30×40×60 cm. Its walls are 1.5 cm thick. It contains 4.0 kg of ice with the remaining space filled with water. The ice and water are in thermal equilibrium. The outside temperature is...

Hi there, I am doing a project modelling and simulating a gas engine waste heat recovery system using an organic rankine cycle. As part of this project I would like to size the surface area of a heat exchanger (if only roughly). I have found the appropriate formula using Q = U.A.LMTD and...

Have a fluid flow in a cylindrical pipe with insulation around it. The insulation is in the shape of a truncated cone. It starts at a thickness with a radius only slightly thicker than the pipe and the radius increases as you move along the pipe. The radius increases at a constant rate. The...

Hello. I am about to show how heat is transferred through crystals i. e metals I know that it should be about conduction, and that the single quantum oscillators start vibrating in higher modes, due to the extra energy. Now is the question: HOW exactly is the energy trasnferred...

\Homework Statement Air is compressed in a piston-cylinder assembly from p1 = 10 lbf/in2, T1 = 500°R to a final volume of V2 = 1ft3 in a process described by pv1.25 = constant. The mass of air is 0.5 lb. Assuming ideal gas behavior and neglecting kinetic and potential energy effects, determine...

Hey guys, first post. I'm trying to determine to the rate at which liquids drop out of a gas pipeline. I've modeled the system in a chemical process program, but its only a steady state model. Anyways, here's some of what I can get out of that program: Heat of vaporization Total Heat Transfer...

Homework Statement A piston-cylinder assembly contains air, initially at 2 bar, 300 K, and a volume of 2m3. The air undergoes a process to a state where it pressure is 1 bar, during which the pressure-volume relationship is pv = constant. Assuming idea gas behavior for the air, determine the...

Hi there, Had a physics project in university that looked at the heat transfer of a pipe in a cement block for snow melting. When I modeled it using computational fluid dynamics, I just did a 2D model and simplified it by saying that the fluid would be moving fast enough through the pipe that...

We have a pan that is used to boil water. There are 2 surfaces to the pan. One is touching the water and the other is touching the stove, obviously. We have heat that is transferred to to pan's bottom. I know what all 3 are and process of elimination tells me this is conduction. Is it...