Heat transfer Definition and 875 Threads

Hello, I will try and provide as much detail to the problem as I can with the hope someone can help me solve this. We are currently working on a wireless project that contains high electrical currents, because of this the box the electronics are enclosed in experience quite a temperature rise...

Hello, I am working a designing a cooking pot with thermoelectrics integrated into the design. I am trying to find the heat flow through the pan to estimate how much electricity the design will produce. First off some constants - The design has a base area of .0491 m2, or a diameter of 25 cm...

If hot air passing through a tube which is exposed to the atmospheric temperature is to be cooled at a certain temperature, fins are installed to increase the heat transfer from the hot air, which one is better design? to install the fins inside the pipe or outside the pipe ? and why?

Homework Statement a small lump of ice at 0 degrees celsius falls to the Earth's surface. when the hailstone hist the surface, all of the kinetic energy of the hailsotne is transferred to thermal energy in the ice. calculate the minimum speed of the hailstone so that it just melts when it hits...

Homework Statement Water flowing at the rate 3.5 kg s−1 through a tube with an inner diameter of 2 cm is to be heated from 20 to 40◦C. If the tube wall temperature is maintained at 90◦C, determine the length of the tube required. Homework Equations Q'=Cp*m*(DeltaT) Q=2*pi*r*L*Q' The Attempt...

Homework Statement A thin flat plate 2m×2m is hanging freely in air. The temperature of the surroundings is 25°C. Solar radiation is falling on one side of the plate at the rate of 500 W/m2. What should be the convective heat transfer coefficient in W/m2°C, if the temperature of the plate is...

Hi everyone. I have here a problem understanding the stability of heat transfer through radiation. I'll give you some background, and later on I'll describe the physical problem. Background I am simulating the unsteady radiative heat transfer between mutually visible surfaces of objects through...

What physical interpretation can we draw from the thermophysical property of thermal diffusivity? How might we visualize the true physical meaning of this property and relate it to its definition?

Hello, Consider this exemple: At y = 0 It is said that the heat is transferred by conduction because the fluid has a velocity equal to 0 (no-slip conditions). But the temperature of the fluid for y=0 is equal to Ts(temperature of the surface) so how come there's a gradient in the temperature...

Hello, PF! Recently, while reading chapter 10 (microscopic energy balances) of the second edition of BSL, I found a minor discrepancy which is confusing me, especially when considering the mathematical analogies of heat and mass transfer. In section 10.1, the authors introduce Newton's law of...

Homework Statement A reversible heat engine produces work from the temperature difference that exists between a mass of m = 9 kg of an ideal gas (cv = 716 J/kgK, R = 287 J/kgK) in a rigid container and a heat reservoir at THR = 285 K. The only heat transfer interaction experienced by the...

Hello, Let's say the temperature of an object is constant and equal to 20 °C. If we put this object to a surrounding which has a temperature of 25 °C, than there's heat transfer from the surrounding to object by convection. If q is the heat transfer (in Watt) than after a specific time (Δt)...

Homework Statement One kg of Refrigerant 22 initially at p1=0.9 MPa, u1=232.92 kJ/kg, is contained within a rigid closd tank. The tank is fitted with a paddle wheel that transfers energy to the refrigerant at a constant rate of 0.1kW. Heat transfer from the refrigerant to its surroundings...

Hello, Heat transfer through finite temperature difference is known a irreversible process because heat cannot be transferred from cold to hot temperature without doing any additional work. But, how this transfer affect the efficiency of the system? How this heat transfer decrease the amount of...

Hello, i have a simple question regarding a problem I am solving. Here it is: A 4x4m flat plate maintained at a constant temperature of 80 degree Celsius subjected to parallel flow of air at 1 atm,20 degree celsius and 10m/s.The total drag force acting on the UPPER surface of plate is measured...

Homework Statement A specific type of ideal gas has a specific heat capacity at constant pressure (cp=cv+R) that is a function of temperature T, such that cp=0.5+876T, where cp has units of J/kg/K and T has units of K. The gas, which is initially at T1 = 294 K and P1 = 1x105 Pa, undergoes a...

Which of the two books would you pick as an undergraduate engineering student if you were to study the subject of Heat and Mass Transfer entirely on your own? 1. Heat and Mass Transfer: Fundamentals and Applications by Cengel & Ghajar 2. Fundamentals of Heat and Mass Transfer by...

Hello all. I want to do some experiment but I thought I would go over this theoretically before trying out and now I have a doubt. Homework Statement I have a driver which produces say 600mA. I connect the driver to one end of Nichrome Wire. And the other end of Nichrome wire is in contact...

Homework Statement How much heat is radiated in water per sq cm, from a block of copper at 250 C and 1200 . Homework Equations e= 0.6 Hr= (Area)(e)(5.67x10^-8 W/m^2K^4)(temperature)^4 The Attempt at a Solution i'm sorry, i don't know how to solve this one...

Homework Statement 1) A typical wall construction for a single-family residence might consist of 0.375 inches of outer sheathing (insulating board, hardwood siding, etc.), 3.5 inches of mineral fiber insulation and then a 0.375 inches inner surface (gypsum, etc.). Typical thermal...

Homework Statement A copper wire has a diameter of 204.3 mil (1 mil = 0.001 in) and a resistance per unit length of 8.31x10^-4 ohm/m. The wire is coated with plastic insulation with thermal conductivity k = 0.20 W/(m K). The upper temperature limit of the plastic is 400 K. The air surrounding...

Two metal rods, one silver and the other gold, are attached to each other. The free end of the silver rod is connected to a steam chamber, with a temperature of 100oC, and the free end of gold rod to a ice water bath, with a temp of 00 C. The rods are 5.0 cm long and have a square cross-section...

Q. Regards infrared radiation, conduction and convection, is infrared radiation the starting point, the fundamental source of heat energy (thermal energy), and the fundamental source of the other two? I’m thinking that the Sun predates the Earth by 30 million or so years so the first heat...

Consider the heat equation dT/dt - aΔT + v⋅∇T = S where S is a source term dependent of the radiation intensity I and the temperature T. The fluid velocity v is prescribed. We also consider the radiative transfer equation describing the radiative intensity I(x,ω,t) where ω is the ray direction...

Homework Statement The ice is placed in water, we know the surface area A, emissivity of both ice and water, Stefan-Boltzmann constant and the temperature of both ice and water. What is the equation for heat transfer rate between water and ice? Homework Equations Heat transfer rate by...

Hello, I am looking for the general direction that I need to go to calculate the following: The time-dependent change of temperature of a finite, but continuous, mass of air moving across a water/air boundary. Let's say you have 150 degree F air moving at 0.007m^3/s over a relatively infinite...

For a general cooler or heater, the calculations for heat transfer are based on the tube side and shell side. So 1) For a reboiler would the vaporizer be the "shell" since that's where the heat transfer occurs? 2) How do you account for the phase change? I used Q = m*cP*dT to calculate duty...

Lets assume an exchanger that is 100% efficient (no heat loss). Duty (Q) and LMTD is known. Your overall heat transfer coefficient (U) is dependent on your transfer coefficients on the shell and tube side, and the resistance of the pipe walls (we're going to ignore entrance effects and fouling)...

Good evening people of PF! I have recently encountered a problem from Himmelblau's Basic Principles and Calculations in Chem. E. which asks to set up an energy balance for a tank, and then non-dimensionalize the differential equation before solving it. It's not the most complex task, but it's...

Hello, my problem is the following: I have an iron bar, which can be heated by convection through an electric cable with power Q. I want to know the temperature of the iron bar after 1 hour has passed, both in the case when the power is turned on and when it is off (Q=0). the input parameters...

Hello, I have completed my bachelors degree in Mechanical Engineering and will be joining for my masters degree in mechanical engineering shortly. I am planning to become a drilling engineer in the petroleum industry. So in order to achieve my goal, what are the recommended courses that i...

If I have a large steel box that is 27ft x 8ft x 8ft and has 7 in thick walls with 4 non-insulated windows each 1ft by 1ft, where does heat escape from inside the box, is it the windows and the walls? So if the inside temperature needs to be 72 F and the outside air is 0 F how much heat would...

Hi, We are doing radiation analysis using solidworks simulation..And as a part of this project i need to validate it theretically..Hope i will get some help here.. Its cylindrical vacuum furnace,where inside strip type heating elements are placed which are connected to transformer of 60kW.After...

Homework Statement A solid, 2.00 kg cube of nitrogen at -220.0oC is added to a 1.00 kg mixture of ice and water at 0.00 oC. If the final temperature of the mixture is -100.0 oC, how much ice was there in the original mixture? Homework Equations e=mct e=mLv/f The Attempt at a Solution...

Homework Statement Getting an expression for the convective heat tarnsfer coefficient. Homework Equations See attached images The Attempt at a Solution I have been reading about the boundary layers. Here is an extract of my notes corresponding to thermal boundary layer and consequently my...

Hi All, I'm trying to understand the radiation mode of heat transfer. I have been reading the book by Incropera - "Fundamentals of heat and mass transfer" and have a few very basic questions. 1) Firstly, thermal radiation is the energy emitted by matter that is at non-zero temperature...

1. The problTfem statement, all variables and given/known data Determine the result when 100g of steam at 100C is passed into a mixture of 200g of Water and 20g of ice at exactly 0C in a calorimeter which behaves thermally as if it were equvalent to 30g of water. Homework Equations FInding the...

hi all i need guidance on how to solve this exercise. thank you all in advance

Homework Statement 1litre of water is heated by an electric burner which couples 500W into the water. How long will it take to raise the temperature of the water to boiling point? How much longer will it take for the water to evaporate?Homework Equations Δu=mCΔT, where The Attempt at a...

Hi, I am currently doing my final year project in college. I am using a copper pipe which is 8m long with 8.5mm ID and 10mm OD. The pipe is bent into a coil which will be placed inside a acrylic box. The aim is to pump water through the coil to get the box to a desired temperature. At the...

So I've been wondering this for a couple days now: Is radiation the only means for decreasing the internal energy of our atmosphere? I know that in kinetic theory the molecules are similar to bouncy balls and if they were in contact with the vacuum of space, the air molecules would have no...

Homework Statement A furnace wall is made up of 3 layers: 1. 4mm layer of material with thermal conductivity of 52 W/m.K 2. 2mm layer of material with thermal conductivity of 20 W/m.K 3. 1mm layer of material with thermal conductivity of 3 W/m.K There is an air gap between layers 1&2 with a...

I am trying to explain the convection heat transfer and the mass transfer related (buoyancy of the heated part of the gas) using only kinetic theory of gases , I mean using only collisions between molecules of the gas. The environment is the usual one : a hot wall in contact with a gas...

Hello guys, I have a problem and I don't know how to solve it properly ... So I have this situation: And I must calculate the heat transfer (Q) through it ... I know that the Indoor Temperature is 21C and the outdoor Temperature is 0C, I also know the following data for all layers...

I need recommendation about heat transfer book . I am having a difficult time learning the concepts. I've tried reading several dfiferent textbooks(e.g. Cengel, Kreith, Chris Long), and though they sometimtes state the same theorem using different wording, different arguments, etc, I am still...

Homework Statement A 0.8m high and 1.5m wide double pane window consisting of two 3mm thick layers of glass(k=0.78W/mK) is separated by a 10mm wide stagnant air space(k=0.026 W/mK). The convection heat transfer coefficients on the inner and outer surfaces of the window are 10W/m^2K and 35W/m^2K...

[FONT=Tahoma] [FONT=Tahoma]1. My Conceptual Questions (5) is at 3. CONSIDER: Case 1: two dissimilar slabs of material (say slab 1 and slab 2) connected in series (bonded at their...

I have to design accumulator of energy. Let's consider insulated cylindrical tank with water. How to calculate all heat losses. Should i consider convection between water and wall and then conduction? but what with all sides of tank? It would be easier with single wall. how to get all...

Homework Statement Two identical brass plates, each 0.5 cm thick, are separated by a rubber spacer of thickness 0.1 cm which has the same cross sectional area. If the outer surfaces of the brass plates are kept at 0 °C and 100 °C respectively, calculate the temperature at each side of the...

I recently installed a water solar heating system for my pool. The pool is 16,000 gallons and the current temperature is 54 degrees. I can get water through the system at 65 degrees at 10 gallons per minute, or slow it down and produce 2 gallons per minute at 80 degrees. Assuming no...