Heating Definition and 590 Threads

If you heat inox steel in presence of air, up to a specific temperature, you get a yellow colour of the metal surface; increasing the temperature it becomes red; still increasing, blue. Is it due to the formation of oxide layers of different thickness? Which effect is responsible of the colour?

Hey guys, Im designing a system where water flows through a copper tube or coil where it is heated and sprayed out the other end. My question is, how does the length of the tube/coil play a role in this heat transfer problem? What I would like to do is pass the water through the inlet at a...

Hi everyone I need to heat up an area 0.5m^3 (100cm x 100cm x 50cm). Would anybody know of any formulas I could use to calculate what wattage heating element id need to heat this area up to 100 degrees C within say 30 minutes. Thanks

I am an ME, looking for resources or advice to assist my team in designing an ohmic heat source. The device will transport hot air with a small fan. We will be utilizing a 120VDC power source. This heater must produce temperatures in the range of 500-1000F. We are anticipating using a wire...

I have this problem and it's something that's been annoying me all day that I just can't get my head around. Imagine a metal block, in direct thermal contact with a heating element and "the surroundings"; but the heater and "the surroundings" are not in direct thermal contact. (I'm supposing...

Hi all, I'm trying to understand induction heating, specifically if there can be inductive heating without a coil, simply power applied through a hairpin-shaped resistor. Imagine a big hair-pin-shaped resistor with power applied to one leg - near the bottom of these legs are small metal...

Could it be possible to heat the people in a house with long wavelength microwaves rather than heating all the air in the building ?

hello, we have learned that according to the laws of thermodynamics that the efficiency of any machine should be less than one because of the passive components in it. in an electric heating machine all the input electrical energy is converted to heat. Does this make the electrical heater as an...

Hello! I am making som calculations on induction heating of a metallic cylinder inside a solenoid through which an AC current passes, but the answer I get seems to be completely unrealistic (10 kW with a 50 Hz, 5 Amps, 230 V rms), but I can't seem to find my mistake. What I think is...

Can anyone give me ideas on how to heat a metal chromed roller to maintain 120 degrees on the outer surface. I currently use a pressurised water heater and a hollow mild steel chromed roller with a 12.5mm thick wall. Can it be done with electric rather than water? The roller has a diameter of 6"...

Is the below calc right? Input electrical power for heating- 4KW Heating time= 20 hrs = 72,000 sec Input energy available= = 288,000,000 J Qty of water to be heated- 7,500Kg Specific heat of water- 4,200 joules/Kg/deg C Delta T in Celsius that can be achieved with the said input...

Homework Statement A flat, uniform cylinder of lead floats in mercury at 0 degrees Celsius. Will the lead float higher or lower then the mercury temperature is raised? Homework Equations None. The Attempt at a Solution Since the mercury is heated, then the density will be lower...

So my question is if I periodically heat some glass of liquid from an arbitrary source, hence providing a driving frequency for the system that will give rise to a phase lag between the temperature of the liquid and the incoming heat from the source, how can I show that there will be a possible...

Hi everyone. I am not sure if this is the best place for this question but here it goes. I am looking to build a small heating element to position in the base of a tank of water. I want to avoid any boiling of the water so want to keep the temperature of the wire at around 90 degrees C. The...

How can I accurately control the Joule Heating effect of a length of Tungsten wire to certain temperature ranges? The tolerance would have to be no more than a maximum of +/- 2°C. Would I require alternating or direct current and/or any other associated instrumentation? I have little or...

Hi All I recently purchased a 1000w heating element for coffee cups, http://www.ebay.com.au/itm/110668421004 that I will be using on a 240v AC source. I would like to know if a cup out of silicone will withstand direct contact with the element? From what I am reading normal silicone...

I'm doing a lecture on electricity for my class and one of the students at the beginning of the semester wanted to know how a curling iron works. So I've never ripped open a curling iron but I assume there's coils of wires within the little 'arm' parts that rely on ohmic heating. However, since...

I have a heating element. This heating element is placed on a wall. If I want the heat to be supplied horizontally would a relflector blocking the top of the heating element work? to prove this are these two statements below correct?? 1. Heat rises so by blocking the top of the heating...

Hello, I am interested to know how pressure affects how much energy is needed to heat up a liquid, if at all. For example, does it require less energy to heat up water at sealevel compared to the energy needed to do the same at the bottom of the sea? Cheers, klillas

If I had an input of 4KW with Material S/S 304 Density(0.29 lbs/in3) Specific Heat(0.12 BTU/lb/°F) What temperature would the S/S level off at when the 4KW is inputted?? If I am missing any info to help solve this let me know...

Right now I am using silver solder to combine heating elements on a copper pipe. This is becoming very expensive. Any other means/materials I could use that could get the similar results as the silver without the high cost!

Hi I'm trying to preform a simple model of a ferromagnetic bar which has a coil wrapped around it. The bar has a 4×4 cm base and is 15 cm tall, the coil has an inside radius of 29 mm and outside radius 30 mm and a height of 10 cm. The goal is to find the eddy currents in the bar, generated...

Homework Statement I know the current distribution through a rectangular cross section of metal. It varies only with respect to y. I need to find a heating function for the metal. (This is only the relevant part of a larger problem). Homework Equations Q=I2R The Attempt at a Solution I...

If I wanted to make bar magnets would I heat up the metal and then place it in a B field of a solenoid and then cool it down in the field to keep the magnetization? It seems if i heated it up first the atoms would be more easily aligned in the B field, And then cool it down to preserve this state.

There are four qualitatively different effects by which microwaves can heat matter: dielectric heating ionic conductivity electronic conductivity hysteresis In most foods, 1 and 2 are of approximately equal strength. 3 can occur in soot particles formed when food burns. In pure...

The resistance per unit length of a conducting wire is proportional to the square root of the ratio of permeability to conductivity. The power generated as heat may be expressed as I-squared x R: also as V-squared / R. In induction, the EMF induced is determined by the rate of...

Would it be possible to use a MASER to vaporize a hole in a cloud? How much would the current best MASERs spread out over a mile? What's the farthest a MASER could be from an an object and still heat it up?

I am looking for some small 30W resistive heating pads, but can't find a supplier who can deliver them quickly. I would prefer somewhere that I can simply order them off the shelf -- anyone know of a company that manufactures/carries something like this? Thanks in advance!

hi i am currently dealing with this problem here: i have some water and want to heat it up with microwaves. how do I determine the change in temperature of the water when i just know the characteristic features of the radiation? is there an equation for it? of course this process is not...

120MJ of heat are used to heat up a 1100kg component from 22oCelsius to 180oCelsius, in 1 hour, prior to heat treatment. If the specific heat capacity of the components material is 500J/kg, calculate the efficiency of the heating process. Please could somone give me the equation that i need...

i hope I am asking this at the right place i just have a few questions... why does it take so much power (115v) to heat up a small coil(heating element) roughly the size of a spring in a pen. what could get just as hot, maybe a resistor? i have a 18 volt battery from a drill and i need to get...

I am solving for the flow of heat on a resistor, say it has a cross-section in the x-z plane and is extended along the y-axis. Fick's Law with internal heating is simply \frac{\partial T}{\partial t}=A\nabla^{2}T+BQ My PDE text gives Q as power delivered per unit volume. So substituting in...

Hi! I need to carry out radio frequency heating (heating by radio waves) for a reaction. Can anyone please help me design a circuit for that?

Can anyone help me/suggest some links to make a radio frequency heating apparatus? I need to carry out radio frequency heating (heating by radio waves) of some reactant samples. Please help..

Hello, I am working on a project this summer and I have run into a problem that I need a bit of help with. If I heat a fluid (water or some refrigerant) in a pipe with cross sectional area A and the fluid has a velocity V through the pipe then how long does the pipe need to be for a given heat...

hi i want formulae for induction heating .. 1) dept of heating 2)power loss per unit volume also for dielectric heating please help me ..

Heating oil: effective or "real" output/yield (per liter) http://en.wikipedia.org/wiki/Heating_oil" says that which is about 11 kWh/L. I was given an unbiased (but not necessarily correct) number that the effective output is about 8 kWh/L ... ... and a potentially biased number (from a...

Is this caused by a lack of nucleation for the gas pockets to be formed or the uneven heating of the water? A clean cup isn't proviingvery many nucleation sites and is it this combined with the even heating meanings the chance of the super heated molecules reaching these sites is reduced is...

Homework Statement In open wide pot exists a certain amount of water, which has mass m=6,5 kg, which free surface has S=960 cm^2. When this amount of water is exposed to Sun, then its temperature gets higher by deltaT=10 K for time t=30 mins. What is the temperature of Sun? Sun radiates as...

I understand that if I apply pressure to water in a closed system, the boiling point increases. So at atmospheric pressure, it boils at 100 degrees C and at 100 PSI, this number increases to 164 degrees C. In my experiment, I'm using the sun to heat the water as it runs through a solar water...

I ran an experiment in which a Daniell Cell (using Cu and Mg electrodes with Cu Nitrate and Mg Nitrate as the electrolytes (both 0.1mol)) was heated on both sides by using two beakers filled with water, the water that heated the cell was heated to about 92C and then left to cool. The experiment...

If a probe entering the Earth's atmosphere heats up because it encounters the atmosphere, then why don't jet airplanes (for example) also get really hot? They are flying around in the same atmosphere that heats up the probe when it re-enters the Earth's atmosphere.

Homework Statement A solar panel (an assemblage of solar cells) measures 58 cm x 53 cm. When facing the sun, this panel generates 2.7A at 14V. Sunlight delivers an energy of 1.0 x 10^3 W/m^2 to an area facing it. What is the efficiency of this panel, that is, what fraction of the energy in...

Homework Statement Two heating coils have resistances 12.0 ohms and 6.0 ohms, respectively. a)What is the Joule heat generated in each if they are connected in parallel to a source of emf of 115V? b) What if they are connected in series.Homework Equations Am I doing this question properly? The...

Homework Statement The aluminum cable of a high-voltage transmission line carries a current 600A. The cable is 60km long, and it has a diameter of 2.5 cm. What is the power lost to Joule heating in this cable? Homework Equations Should I use the equation V=1/(4piEo)integral(dq/r) to...

Hi there, I've been interested in this induction heating thing and would like to build one. Its quite a long time searching the net and experimenting to make it work. I've been stuck with the pll issue. My configuration is Hbridge which is fed from a simple power supply(not split) so the lowest...

Why do substances expand on heating? Please give an understandable molecular account of the process of expansion.

Homework Statement Coffee maker, whose output of 650 W, producing coffee. Kettle to the boil 5.0 dl of water, with an initial temperature of 14 ° C. Heat capacity of water is 4.19 kJ / (kg ° C) and water density of 1.0 kg/dm3 Homework Equations How long does it take a coffee water...

I need a solution for healing tree grafts. Fruit trees are often propagated in the spring by grafting (attaching) a piece of scion wood to rootstock. The graft must "heal" which means that the outer "cambium" layers of the two pieces join together. This process occurs around room temperature...

Homework Statement Say we have a warehouse with a 5 hr time constant. The outside temp is 16C at 2:00AM, and 32C at 2:00PM. The warehouse is at 24C at noon. What will the temp be at 6:00 pm? When will the temp be 27C? The Attempt at a Solution First, I set up a sine wave for the...