Heat and mass transfer Definition and 39 Threads

Hi all, I've started working recently in a new job as an engineer in a lab with a bunch of physicists. A job they've given me is to size a water/glycol chiller (and basically design the hydraulic system i.e. fittings, tubing etc) to cool a bunch of equipment they've got in a few insulated...

What is the difference between the approaches of Einstein, Debye and Peierls regarding the heat transfer?!

Summary:: Determine the temperature distribution in a bar (very long– 2D) with rectangular cross section, in steady state, with imposed flux at one face, convection at the opposing face (Tinf, h), and imposed temperature (T1) at the two remaining walls. I am trying to find the analytical...

Hi and thanks for taking the time to read my question. So, if i take an element and place it on top of another element and heat it, will the heat energy pass through the first and charge the other or it'll melt both elements? Thanks!

there's a website to size an aquarium heater or chiller. This is just for learning purposes (not for fish) but I have modified these parameters from default to perform a load calculation on a 100 gallon glass tank... For the tank temperature range I set to be between 150-160 degree F. and a...

Hi guys, I am confused about the heat transfer mode of between two contacting material, especially in a channel flow. Obviously, conduction or convection dominate the heat transfer process in the process with low object temperature . But I am not sure if I have a fluid of 500 Kelvin, flowing...

If a substance gains energy, it's molecules vibrate faster and thus the material increases temperature. My question is if heat lost through any other means but radiation is zero, how exactly does these molecules radiate photons?

Hello, I am a Mechanical Engineer a little out of practice on Heat transfer. I am trying to solve this problem. It must be solvable but i have yet to find right equations online. I have a multi Layer Cylinder made up of C350 marraging Steel,Zinc Alloy-12 , then 6061 Aluminum T6. All that is...

I am trying to run a calculation to work out the overall heat transfer coefficient of an arbitrary ten plate exchanger where the fluid is not determined using Re=puD/mu where mu is dynamic viscosity. When mu is such a strong function of temperature how should I determine which valye to use, say...

Why I cannot get the right answer by using △T=(3/2)nK△T to solve problem C：

$$\frac{\partial T}{\partial t}=\alpha\frac{\partial^2 T}{\partial^2 t}$$ with an initial condition and boundary conditions $$T(x,0)=T_0$$ $$T(L,t)=T_0$$ $$-k\left.\frac{\partial T}{\partial x}\right|_{x=0}=2A\cos^2\left(\frac{\omega t}{2}\right)=A(\cos\omega t+1)$$ where $A=V_0^2/(8RhL)$...

Hi all, Ameya here from the University Of Twente Netherlands pursuing masters in electrical Engineering. Currently doing my thesis. My topic involves developing a biomimetic sensor.

In context of heat transfer, are conduction and diffusion same process?

Homework Statement If you have a heat exchanger with a cooling fluid and a fluid that condenses, and the fluid condenses over the entire heat exchanger i.e. its temperature is constant. How can one make a heat balance in such a case, when dT is 0 for the condensing fluid but not the other? i.e...

Hello, I have a transient heat transfer analysis question where I heat a plate for a short duration and then evaluate thermal response. The duration of heat pulse occurs for .1 seconds at time t = 1 second and thermal response time I would like to evaluate is 1 minute. I use an Ansys APDL table...

we planning to heat water directly using microwave for industrial purpose. we need only 33deg Celsius for that I need this.

I am looking for a graduate level textbook that would sufficiently describe the two phase flow characteristics during flow boiling. What textbook could I use to explore this topic? Is a graduate level forced convection going to cover two phase flow?

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...

Homework Statement A plastic pipe (k=0.092 W/m.K) of inner and outer radius of 1 and 1.25 cm, respectively. If the inner and outer surfaces are at 60 °C and 30 °C, respectively. The rate of heat transfer per unit length is close to: a) 98 W/m b) 89 W/m c) 78 W/m d) 168 W/m e) 112 W/m...

Hi, I would like to ask you for advice with a problem, I'm working on. I have a regular shape object (glass cylinder) in which is the 100W heat source. The heat source is ind the middle of cylinder and radiates heat uniformly throughout it’s height. Heat, of course, gradually moving into...

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...

It appears very non intuitive to me seeing TS diagram of vapour compression system; Area under the curve increases. But how seriously how higher evaporator temperature will lead to higher refrigeration effect. Refrigeration effect means lower temperature.

I have a doubt regarding gibbs phase rule in thermodynamics.. It says the number of independent intensive properties required to specify the state of a system is F=C-P+2 where C is number of components and P is the number of phase.. So for a water and water vapour system, C=1, P=2 . So F=1. If...

Hello, I am trying to achieve a range of temperature (below 0 degC) by heating up liquid nitrogen (77K) with an electric heater (100W) inserted into a copper block. How do I calculate the time taken (t) for the nitrogen vapour to reach temperature T (say 100K). The liquid nitrogen is poured into...

I am not a mechanical engineer; but I have physics background. I want to lift about 250 watts of heat from a metal block. At the same time I have to maintain its temperature at 30 deg Cel. For this I want to use water-air heat exchanger (HE). Heat exchanger will have inlet & outlet pipes. Hot...

I've been tasked to see if I could determine the number of chill rollers needed to cool down glue being extruded onto a fabric. I'm not sure if my method is valid. The roller has wall thickness d with contact area A. Water inside chill roller is at T1 and glue is at T2. 1) Calculate the rate...

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...

Homework Statement Problem data:[/B] http://imgur.com/a/hEz16 Homework Equations Rconduction=ln(rout/rin)/2*pi*Length*thermal conduct Rconvection=1/2*pi*Length*routside*convective heat transfer outside =>Qconduct=2*pi*Length*thermal conduct*(Tin-Tout)/ln(rout/rin)...

Homework Statement Hello, I am struggling with this heat transfer and fluid flow problem.I would really appreciate if someone could have a look over what I have done on it. I am not sure if what I have done is correct ,I would really appreciate if you could tell me if it is correct or wrong.And...

Hello, I have here a complex question. My background is Chemistry and Optoelectronics. I wasn't the best when we were studying Thermodynamics at uni so I have some knowledge-gaps. Anyways, here is my problem. Can somebody explain me the whole process of the convection in the coffee roaster. So...

I am trying to find an expression for the average Nusselt number corresponding to heat transfer from an isothermal disk. Given: ShD≡hm(r)D/DAB=Sho[1 + a (r/ro)n] (1) Sho=hm(r=0)D/DAB=0.814ReD1/2Sc0.36 (2) Relevant equations: Average nusselt number is defined as Nuav=havD/k where k...

I'm designing an oven and want to ensure that the insulation I specify has a low enough Thermal Conductivity (k) to resist excessive heat loss. I determine heat loss (Hout)with the following equation: Hout=A*U*(T1-T0). U is dependent on k (U=k/L). I omitted the heat transfer coefficient in...

Hey guys, I'm really stuck right now 1. Homework Statement Habitable exoplanet: Now we will include a convective heat flux (H), with H being proportional to the difference between the atmospheric and ground surface temperature, $$H=c_p(T_a-T_p)$$ with c = 1.2 Wm−2K−1. Calculate the temperature...

Hi all, I'm a ME graduate student concentrating in fluids and I'm trying to decide between two electives. The two I'm looking at are Nonlinear Control Systems or Advanced Heat Transfer. Nonlinear controls looks interesting, but I'm not sure how it could tie in with fluids...as opposed to heat...

Hi guys, I have functioning MATLAB code for my solution of the 3D Diffusion equation (using a 3D Fourier transform and Crank-Nicolsen) that runs just from the command window and automatically plots the results. However, it seems like my solution just decays to zero regardless of what initial...

I want to design a water heating system for a special type of pool. The system is open-loop, where input water at 10 C has to be heated to 15 C, and then enters the pool and is eventually exhausted out of the pool. The flow rate is about 100 litres/second (6000 litres/minute). Simply heating up...

Homework Statement A pipe of internal radius r1=0.03 m is built to have conductivity variable with radius: k=ar2, where a=250 Wm/K. 1) Find the critical radius r2 for the maximum heat transfer by convection from its external surface if the heat transfer coefficient is h2=30 W/m2K. Homework...

Homework Statement Heat capacity is the ability of the material to store energy internally. If I completely insulated diamond and I put heat into it, It would have the ability to store 6.57 (Joules/mole) per degree Kelvin. Use this formula q=Cp (ΔT/ Δt) where q is heat in Watts, ΔT is...

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...