Heating Definition and 590 Threads

I have a question in regards to a specific situation and really don't know which elements are significant. The example is high pressure AIR (a real gas/ not ideal ;-) of relatively unlimited volume, released via a rupture diaphragm into an enclosed tubulation. (dead ended) Relative dimensions...

if I heat a resistor, it will reach a specific temperature and keep it. because as temperature increases the resistance decreases, so reducing the power absorbed. is that true? and how to calculate how much current and voltage I have to deliver to reach a specific temperature?

Hi everyone, I'm struggling to understand what I think is a very basic concept: Joule's law of heating. Allow me to explain my confusion: We know that voltage can be expressed as: V = I · R And power can be expressed as: P = I · V Making power equivalent to: P = I2 · R According to my...

Homework Statement An electrical heating element is to be designed so that the power dissipated will be 750 W when connected to the 240 V mains supply. (a) Calculate the resistance of the wire needed. (b) The element is to be made from nichrome ribbon 1.0 mm wide and 0.050 mm thick. The...

Hi All, I'm working on a process involving induction heating. I'm heating up an irregular shape ss die to make a bond. My dilemma is in my understanding of where the eddy currents will be that generate the heat (based on skin effect). The clam shell die is pictured below. The right hand...

Hi everybody! I was wondering, what substances do form when plastic is heated? I found on the internet that if plastic is heated in the oven (not microwave) at 325°C, it shrinks and become more thick, and it can be used for art work. I tried to search about it, but I found different opinions...

Homework Statement A domestic kettle is marked 250 V, 2.3 kW and the manufacturer claims that it will heat a pint of water to boiling point in 94 s. (a) Test this claim by calculation and state any simplifying assumptions you make. (b) If the kettle is left switched on after it boils, how long...

Homework Statement [/B] We are heating a semi-infinite slab with a laser (radius of a stream is ##a##), which presents us with a steady surface heating (at ##z=0##), everywhere else on the surface the slab is isolated. How does the temperature change with time? Look at the limit cases: at ##t...

Suppose a laser beam polarized arriving from vacuum to a medium. What are the reflexion and transmission powers taking into account heating. What equations could be used to solve this ?

If I have underfloor heating, whether the materials which is a better insulator on the floor (eg.a wood in relation to the ceramic tiles) affect on higher energy losses? Or the entire system will be more inert? It is assumed that the whole house is well insulated? I'm also interested in the...

Hi folks, I want to build a heater similar to this http://www.thermon.com/us/products.aspx?prodid=10 , using a ZVS power supply from ebay (such as this one -http://www.ebay.com/itm/381569526996?_trksid=p2057872.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT) ) As well I would like to replace...

Electromagnets heat up quickly...shouldn't heat destroy its magnetic properties?

Hi Everyone, I will try to keep this short as I can and to the point, there is a bit of a back story, so bear with me. For the last 18 months (on and off as life allows), I have been trying to develop an induction heating assisted machine for 2 reasons. 1 - To learn as much as I can by doing...

I'm talking about how like the atoms expand and the electrons get farther away from the nucleus. This might be a stupid question but how does that make it less magnetic? Like what do the electrons being farther away have to do with how strong the magnet is?

If you shine two lasers at the same spot that are the same frequency, and; exactly out of phase; would there still be energy at the one spot they are pointed at?

I'd posted more of a real world version of this question, involving greenhouses, a few days ago at... https://www.physicsforums.com/threads/is-greenhouse-interior-much-cooler-if-reflective-inside.875575/ ...but with no responses after 130 reads, I'm reducing it down to a barer and much better...

Hi I need help with this question, because I find it a bit confusing, thanks! Suppose we have a steel sheet with a circular opening, and a sphere with a diameter equal to that of the circular opening diameter. If we heat the steel sheet with a match or any heater, then which of the following...

I know it is many threads here about this topic and I've read most of them. But I have next questions, next step :) 1) (Summary) Does it true that composition and structure drive an energy levels of electron and it absorbs such wavelengths which correspond to jump to upper (not implicitly...

I've come across this floor heating mixing unit from Watts in an appartment. The image shows how things flow (I could only find this with some russian-looking annotations). To the left of the return connection there is a water meter - not an energy meter - it only shows the accumulated amount...

Homework Statement Water is contained in a cylinder fitted with a frictionless piston (figure shows that atmospheric pressure acts on piston from above). The mass of the water is 0.45 kg, and the piston area is 0.186 m2. Initially, the water conditions are 110oC and 90% dryness fraction, and...

When I plot the isenthalpic curves in T-P plane, I see isenthalpic curves are not well defined in the lower temperature region in T-P plane. Inside the inversion curve Joule-Thomson coefficient is positive so gas cools and outside of the inversion curve Joule-Thomson coefficent is negative so...

a) how much more heat is used to boil 237 mL of water as opposed to starting the car? b) what major concept/finding was overlooked while solving this problem? I think this has something to do with delta H = mc(delta t) but idk

I have a flexinol wire, and it has a resistance of 0.11 ohms/inch and it requires 4000mA for a 1 second contraction. I was wondering how much energy was required for a 1 second contraction and if I were to heat the flexinol under a vacuum, how much less energy would be required. The flexinol is...

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...

`After a charge carrier loses kinetic energy in a such a collision, the force due to the pd across the material accelerates it until it collides with another positive ion.' I got this from a book, can someone explain this in a simplest way.

Microwave oven operates at 2.4 GHz. Consider the situation of making tea or coffee in Microwave where water is heated to 100C to boil. Looking at Planck's law / Wien's law, 100C (373K) corresponds to a peak wavelength of 7.8nm or 38.6THz which is in Mid Infrared. Effectively materials...

Wasn't sure whether to post this here or in EE forum. I've been learning about induction heating for the past few hours and scoured every video on youtube and every web article I could come across and I still lack an understanding of how to determine the heat output of an induction heater. I...

Hi, I want to heat magnetic nanoparticles in an AC magnetic field. I need a uniform and a magnetic field about 15- 25 mT ) . I have thought about some designs, can you tell me which one is the most suitable design for creating a uniform alternating magnetic field? I need this system for...

Hello, first of all, I understand, how microwave tube works but I'm interesting in how exactly the microwave heat up a things? What's the matter inside. I have heard about increasing energy of molecules of water by polarization them by micro-wave. But I have got a plate which is not from...

I know that peltier plates are for cooling(mostly :smile:) but I wish to try out heating other substances using peltier plates. I'm planning to use 3 peltier plates (TEC1-12712) [maximum temperature difference of 70 degrees measured at 25 degrees / Maximum temperature difference of 80 degrees...

i wanted to know if it's possible to run a heating coil which reaches some 300 C and a dc motor of low rpm of some 10 or so...and all this under 250 W??

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...

Hello, I need help with defining pressure in closed district heating system. As shown in attached drawing, we have a heating station which supplies hot water (110/70 degrees C) to various households. The lowest house is 90m below station and the highest one is 20m above. I need to determine...

Hello, Me and my buddys doing aproject on Heat transfer. we choose wall heating as our subject and we have some issue on modeling the system. our system is : two walls, one exposed to the atmosphere the other is the house wall. between them there's a pipe with hot water and some aire. we...

I have a 40x60 by 14 foot garage... 3 walls are R19... one wall maybe about a R10 (garage doors, somewhat well sealed) ceiling is R30... (how would I calculate in BTU for raising the temperature from 40 degrees F to 60 degrees F in say four hours with an outdoor temperature of 20 degrees with...

On average it takes about 30 seconds for hot water to reach the shower, so for 30 secs water is being wasted. I know running water for 30 seconds doesn't seem that bad but there are a lot of water shortages and droughts going on all around the world. I know its possible to heat water with 9v...

Hello. I want to calculate how long time it takes to heat an object with radiation. The object is the inner cylinder of two concentric cylinders. The inner cylinder is not hollow. If assuming black body: \dot{Q}_E=\sigma A_1(T_1^4-T(t)^4) [1] Energy emitted must the same as the energy...

If I am rotating an object into the ground ( drilling machine) how can i convert all the heat into something useful without wearing the drilling machine? without using drilling fluid to cool it down. like should i use certain materials that can resist the heat from friction or can i like use the...

Hello, I am trying to determine the thermal conductivity of a material based on the following information. ##Q_x = - k \frac{dT}{dx}## Temperature as a function of ##x, T(x)##; ##T(0) = 15## ##T(0.1) = 10## ##T(0.2) = 5## ##T(0.3) = 3## and finally that ##Q_{x=0} = 40 \mathrm{Wm^{-2}}##...

Hello, Why do self regulating heating cables have such low power output per foot? Power output in these cables does not exceed 20 W/ft at 10 degree C, and decreases as the temperature goes up. Many of the cables I saw can withstand high temperatures (250 degree C power off and 150 degree C...

I have very little knowledge when it comes to physics. I'm trying to heat up a guitar string using electricity. The power source is 5 amps and only slightly heats up the string. I need a wire to get hot enough to cut through styrofoam. Please help with wire and power source suggestions.

Hello friends, The balanced chemical equation for the combustion of carbon is: C(solid) + O2(gas) -> CO2(gas) Now, the lower and higher heating value of hydrocarbon fuels (such as methane) exists because in the LOWER heating value, you are subtracting away the latent heat of vaporization of...

We have LED arrays for visible lighting. What problems exist for using infrared LED arrays as a heat source for humans, like those in a residential settings? Does effectiveness vary much by wavelength and skin color, clothing worn, etc? Thanks. :-)

Hello, I know there is a similar topic but it has been closed. It is about a wind turbine that generates wild AC from 0 to 240V(open voltage) for a maximum of 1500W. Instead of using a charge controller, a battery bank and an inverter I would like to connect a water heating element directly to...

Hi, I am having a hard time answering this question. Any help will be appreciated. In 1938, the journal Nature published a paper by R. Emden titled “Why do we have winter heating?” (Nature Vol 141 pp. 908-9 – although you do not need to read it to answer the problem). This article asserts that...

Hey everyone, I had a few questions about resistance of wires and heating. I'm a materials engineer looking to replace traditional copper with something more lightweight, however, the alternatives have high resistance. For comparison say copper wire has .01 ohm/ft the other material could be 1...

Moderator's Note: THIS HOMEWORK WAS POSTED IN ANOTHER FORUM, SO THERE IS NO TEMPLATE. calculate the change in entropy suffered by 2 moles of an ideal gas on being heated from a volume of 100L at 50C to a volume of 150L at 150C. for the gas Cv=7.88 cal/moleC. I'm really confused in entropy and...

Homework Statement This is not entirely a homework question but more a question about a homework assignment. We were asked to find out why a filament of a bulb heats up by talking about microscopic ideas. This is a link to a website that contains the relevant information under the heading...

Hello Forum, Most devices that are supposed to generate heat via resistance are connected to a constant voltage source. That means that the amount of power dissipated as heat is given by P= V^2/R = I^2*R This implies that the smaller the resistance the larger the current through the heating...

Hey guys!, I just want to know what will happen when you heat up lanthanum hydroxide La(OH)3 from 20 degree Celsius to 900 degree Celsius in a furnace with O2 gas. Is the mas of La(OH)3 increases? and why? thanks in advance!