Heat transfer Definition and 875 Threads

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...

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...

Homework Statement A 1.0 cm diameter steel rod with k = 20W/(m-K) is 20 cm long. It has one end maintained at 35°C and the other at 100°C. It is exposed to convection heat transfer with h=65W/(m^2-K) and an ambient air stream at 20°C. a) Sketch the distribution of temp within the rod. b)...

Hello Everyone, The question I am about to pose concerns something I may possibly already have an answer; however, I would like to proceed with posing the query, that I might solidify my understanding. If a system transfers heat to its environment, does this necessarily imply that the...

Homework Statement Homework Equations d/dx(kdT/dx) + S = 0 (for steady state) q_cond = -kAdT/dx q_gen = S*Vol The Attempt at a Solution So I tried to equate q_cond to q_gen but it seemed to give me the wrong answer. Does anyone know why? I believe to get the right answer I have...

By oversimplifying the problem I have, imagine that I have a panel constructed of stainless steel flat walls. The dimensions are 80 in x 70 in x 20 in, and the thickness of the panel is 1/8 in. Inside, I have a heater that outputs 400W of convective heat. The temperature inside the panel is...

Homework Statement I am curious about the situation of heat transfer between parallel horizontal plates in an enclosed space (particularly with the lower plate being higher temperature and subjected to a steady heat flux) with the enclosure itself being composed of a fictional "perfect...

Here is the solution to the problem, all you need to look at is the diagram, the conductivity values and the graph. What I don't get is why the temperature is not continuous when the material changes. Shouldn't there be equilibrium at the boundaries between the different materials?

Homework Statement Homework Equations (unsure) The Attempt at a Solution Homework Statement Homework Equations The Attempt at a Solution

What is the difference between constant wall heat flux and constant wall temperature for convective heat transfer correlations?

how to reduce temperature of a solid bar from 550°c to 450°c by water spaying... someone really help me...??

Suppose you have a cylindrical rocket engine with surface temperature T and you want to measure temperature on the inner wall T0 of the combustion chamber (assume 1 dimensional heat transfer). The chamber has thickness d, and heat transfer coefficient k. If combustion is assumed to occur...

so I'm told that temperature difference is ultimately what results in heat transfer. But when considering what happens inside a uniform material, if temperature difference was solely responsible for heat transfer, then different heat transfer rates wouldn't exist among different materials at the...

I was hoping someone could lend a hand with a question about thermodynamics. It's been years since I've done work on thermodynamics. Let's say I have a plastic 275 gallon liquid container, filled with a mixture of Propylene Glycol and Water (50/50 by volume). The container is placed inside of...

Homework Statement What mass of water at 25dC (d = degrees) must be allowed to come to thermal equalibrium with a 1.85kg cube of aluminum initially at 1.5*10*2dC to lower the temperature of the aluminum to 65dC? Assume the water doesn't turn to steam. Homework Equations Q = Del(T)m(C)...

Homework Statement The world's most active volcanos, such as the Kilauea volcano in Hawaii, can disgorge about 5 ✕ 105 m3 of 1000°C lava per day. What is the rate of heat transfer out of the Earth by convection if this lava has a density of 2800 kg/m3 and eventually cools to 32°C? Assume that...

Hello. I'm a student of Univ. of Korea. As you can see in the attachment, I'm calculating the Temp variation in 2-D. The node 24 has a convection from left upper quadrant with h, a conduction from right upper with k1 and a conduction from bottoms with k2. I can't figure out how should I...

Have a new task, would appreciate some pointers. Conducting a heat transfer analysis on a tank with water coming in and out that's to serve as a hot side for a displacing stirling engine. If the inlet q dot into the tank is 1000W. Observing there will be losses due to conduction and...

Homework Statement Homework Equations The Attempt at a Solution I am not sure about the relevant equations to be used here. At first sight, I thought I had to apply Stefan's law but then, the question states the power consumed by bulb, not the radiated one. I am completely...

Homework Statement What is the expected temperature change during one second of a polypropylene solid with mass 0.1 g at 105 degC to air at 20 degCHomework Equations heat transfer: Q= c m (T1-T0) where Q = amount of heat c = specific heat capacity = 1.8 J/g/K m = mass T1-T0 = change in...

Homework Statement Derive a differential equation (do not solve) for the temperature distribution in a straight conical fin. Assume one dimensional heat flow. This equation is assumed to be 1-D steady state conduction. Homework Equations For this problem, we can use the generalized...

Hi Guys, can I get some advice on how do I get started on the question? I'm guessing that natural convection is the key to solving the question. but i have no idea on how to solve it.

Hey guys. I've been cracking whole day over this question to no avail. I mean I have no idea if it's correct or wrong. And I desperately have to get it done by tomorrow and it's already midnight here so would really appreciate any sort of help I can get. Here are the doubts that I'd like to...