What is Cooling: Definition and 639 Discussions

Being that both laws explain some kind of heat transfer I was wondering if they are in any way related.

Why is it that two spheres,one hollow and other solid having same material and size and heated to same temperatures cool differently? Precisely,why does hollow sphere cool faster than solid sphere?

A hot object cools down to a temperature of 10 degrees of Celsius during a period of 180 seconds. The room temperature is 10 degrees of Celsius. Assume the coefficient in the Newton's Law of cooling to be 0.01[1/sec]. Determine the original temperature of the substance 2. T(room) +...

For a sensible air cooled heatsink, what is the maximum wattage a nuclear reactor could be?

Hello everyone, I have a question regarding the rate of cooling for the CMBR. I understand that the rate of cooling is directly related to the rate of expansion of the universe, but I lack the mathematical prowess necessary to make any use of this. I am specifically trying to determine...

I`ve read that in thermoelectric cooling the current passes through a two different materials and because electrons start to slow down and radiate heat cooling is acheived. But why not to use in this case a usual resistance instead of expensive metals? For example we will place coper wire...

Dear Fellows, Well, i am working on a power plant and i need to analyse the Cooling Water Piping Circuit (Supply/Return piping), i.e., from Turbine Surface Condenser to Cooling Towers and from Cooling Water Pumps to Turbine Surface Condenser. The Lines are huge around 52" NPS and are buried...

Evaporation is a cooling process. What cools and what warms? Also, condensation is a war,ng process. What cools and what warms? I understand that during evaporation the water molecules of water slow down therefore cooling down. But does this mean that the air warms up? The opposite goes for...

Homework Statement A cooling bath is prepared in a laboratory by mixing chunks of solid CO2 with ethanol. CO2(s) sublimes at -78.5°C to CO2(g). Ethanol freezes at -114.5°C and boils at +78.4°C. State the temperature of this cooling bath and describe what will be seen when it is prepared...

Conventional thought in the gun forums is that a rifle barrel that is smaller in diameter will cool faster than an otherwise identical gun barrel that is larger in diameter, after the same number of shots fired. Is this true? I have trouble understanding how it could be since the larger...

Hello, I am trying to cool down an electronics cabinet using air at various conditions (Temperature). The cabinet contains components on the inside and each has an inlet and an outlet. The outlet is a circle hole or "orifice". I need to determine the size of the orifice to achieve an outlet...

Homework Statement One mole of a liquid with a constant molar heat capacity of 132 j/mol K is initially at a temp of 80 C. The heat capacity is independent of tempearture. Calculate the maximum work that could have been done onthe surroundings while cooling the liquid reversibly. The...

Homework Statement One mole of a liquid with a constant molar heat capacity of 132 j/mol K is initially at a temp of 80 C. The heat capacity is independent of tempearture. Calculate the maximum work that could have been done onthe surroundings while cooling the liquid reversibly. The...

URGENT! Newton's law of cooling to find time of death Homework Statement The victim, Peter Sloane (a senior physics lecturer), was discovered at 9.43pm with a liver temperature of 22.26°C in the Oliver Lodge coffee room, with the window open. The temperature of the room matched that of the...

Hi, I refer to this Wikipedia article http://en.wikipedia.org/wiki/Resolved_sideband_cooling I understand how everything works except for one detail. When the atom is moving towards the laser, the laser frequency is Doppler shifted such that its frequency matches the energy gap \omega_{0}. So...

For contra-rotating motor, the external rotating element is a cylinder that carries copper coil and on account of electrical resistance, the coil is getting heated. The generated heat can be removed only by circulating oil around the coil through cavities/vents available inside the cylinder that...

In several papers, diagrams, etc. about atomic experiments I saw pairs of lasers beaming in opposite directions. Naive question: why two lasers are used instead of one and a mirror? Or even further: why six lasers are used (2 in each axis) instead of just one and bunch of mirrors?

Homework Statement A cube of copper of mass 4 kg and initial temperature of 110 oC is set to radiatively cool in an environment of 100 oC. (Note: copper has an emissivity of about 0.05. Also, neglect conduction and convection as cooling agents in this problem.) The surface area of the...

Hello, I am currently studying transformer design, in particular cooling methods. I am tyring to calculate the cooling effect (increased heat transfer) of adding cooling fins to a transformer. Does anyone know of some general equations/methods for calculating the increased heat...

I am a little confused about how exactly the CMB "works". At first hearing, it makes perfect sense that as time goes on and the universe expands radiation would decrese in frequence, but when I think about it a little more deeply I miss something. My thought is how exactly does the light...

Homework Statement your 200 gram cup of tea is boiling hot. About how much ice should you add to bring it down to 65C? Ice is initially at -15C. The specific heat capacity of ice id .5cal/gC The Attempt at a Solution So the ice we add needs to absorb 7000 calories of heat. Heat...

Hey, I have this math investigation task which asks us to model the cooling of coffee in three different cups over a period of time. Anyway, i got the data, did a scatter plot and found the exponential model, but i don't know how i could determine which one has the greatest rate of cooling. I...

Einstein's Refrigerator - Cooling Agent & Size Matter?? I'm looking at Einstein's patent #1,781,541 for a closed non-mechanical refrigeration unit approved Nov. 11, 1930, filed Dec. 16, 1927. http://www.fourmilab.ch/etexts/einstein/uspat1781541/www/" I'd like to power it with the solar heat...

Vacuum+Water= cooling.. maybe?? hello everyone first I would thank you for this wonderfull forum I was only reading for along time and learned a lot. today i would like to present an idea about vacuum cooling or evaporative cooling i don't know so here it is: 1) vacuuming the air from a...

1. LAW OF COOLING PROBLEM!HELP PLEASE! :) At 1:00pm, Sally puts into a refrigerator a can of soda that has been sitting of temperature 70degF. The temperature in the refrigerator is 40degF. fifteen minutes later 1:15pm, the temperature of the soda has fallen to 60degF. At some time later, Sally...

I'm hoping I'm in the right forum for this, but here's my question. Optical cable can guide radiation to a point, which is the basic of my thoughts. Say you had an insulated box. On the inside of this box, is a liter of water in the shape of a cube, giving it a surface area of .06m^2. From the...

Hey all, Bear with this stupid question. So I noticed that my apartment is currently 85 degrees, and my tap water is currently 65 degrees. I looked up the volumetric heat capacities of water and air, and found that water has approximately 3200 times the Joules/(Kelvins * cm cubed). So if...

Alright so I have been bored this summer so decided to take apart my electronics such as my Xbox and AV receiver. I installed a nice 12vdc computer fan on the side of my Xbox so I moved onto my AV receiver and then ran into some problems. My current set up consists of: 2x - 12vdc computer...

Homework Statement at t=0; thermometer reading (x) =80 F (taken outside where the air temp is 20 F) at t=3; x=42 F then the thermometer is brought inside where the air is at 80 F. at t=10; x=71 F When was the thermometer brought indoors? Homework Equations temp=ambient temperature; x= present...

Hey, So I'm trying to figure out how effective evaporative coolers are... Lets say, I have a box with 3 cubic meters of air with a humidity of a 10%. I blow it out with a fan and spary with water as it leaves the fan. The water is room temp (which is let's say 27 C). What temperature...

By heating a gas inside a cylinder, you allow it to expand against a piston while maintaining a constant temperature. The energy that you add as heat goes into the PV work of the gas against the piston. To start again, you have to push the piston back to the start point, compress the gas...

I am analyzing the lengthwise temperature distribution in a cooling fin (length: 30mm, width: 10mm, the tip is assumed to be adiabatic, Biot number is smaller than 0.1). When I try to calculate the dimensionless temperature distribution (see calculation below), I obtain a curve which has a...

Can you "move" particles by cooling them? Suppose you have an object made of particles and you cool it down alot. I would assume then that the average momentum of the particles would be reduced therefore we could know more about the particles' momentum and therefore less of the particles'...

Hi I keep reading that an atom cannot be cooled to v=0 because of random recoil from spontaneous emission, i.e. a random walk in momentum space. If it is a random walk, then - on average - we don't have any net motion, i.e. we stay at the initial position. This also holds in momentum...

Hey all, I am trying to construct a peltier device where the 'cold side' can cool down to about 10 degrees C. I want to be able to run the device for upwards of 30 minutes but I am not sure what heat sink to use to remove the heat from the hot side. Any suggestions on what heat sink to...

A natural draught cooling tower is designed to have a 3% loss of the mass of the water entering the tower by evaporation into the atmosphere. Atmospheric air enters the tower at a volume flow rate of 4 m^3/s a temp of 10C and a relative humidity of 50%. Air leaves the tower in a saturated...

Homework Statement An hot object is positioned on a slab at room temperature (20° C), which of that 2 ipothesis is correct? 1)The object will get cold because of the conduction with the slab, the convection af the air around the object and the electromagnetic radiations it send out. 2)If...

can i kw why Newton's law of cooling is used for estimating the time of death? what are its advantages and disadvantages?

Liquid cooling PCs, why so expensive?? So I was thinking about getting a new computer which means new water cooling system :D teehee! I was pricing out systems and noticed that some are just so ridiculously expensive. For example, looking at the components vs. stuff I can find on amazon...

Hi All, I am hoping to create an equation which I can use to describe the thermodynamic properties of microhabitats used by Chuckwalla lizards. Basically,the habitat in question is a crevice that is shaped like a rectangular prism within an igneous rock. I am trying to develop an equation that...

Hi :smile: Tomorrow I will be performing an experiment trying to prove that the Rate of cooling of water is directly proportional to the excess temperature5/4 I am going to be recording the change in temperature over time using a data logger and record the temperature of the room...

Just pondering Eric Agol's recent paper on White Dwarf habitable zones and the pace of cooling of white dwarfs (WDs.) He uses models of Carbon core WDs with helium atmospheres, but I am wondering if pure helium WDs would last three times longer. Opacity from the atmosphere slows down heat loss...

I would like to ask why the cooling capacity of air-conditioner is 2-3 time more than the work done by the compressor?? According to the conservation of energy, the amount of work input should be equal to the amount of heat absorbed(cooling capacity), isn't it?? Can anyone explain it...

Hello and here is my problematic 1st post. I have a problem which i need help with, I'm an electrical engineer so my understanding on this subject is basic. I need to calculate the cooling effect of a AGR fuel pin and I'm not sure were to start. Here is some background on the question...

Hello, I am far from nuclear plant engineering, so I might be asking irrelevant question... But I was wondering, why the Fukushima power plant reactor cooling system was designed to be dependent on external power? That sounds like planning for failure to me, especially in the environment...

Could anyone who actually works on this kind of thing answer a couple of questions about the current situation in Japans nuclear crisis : Is it true that cooling pools for spent fuel rods are stored on the rooves of these reactors ? If so we see two of these rooves have been blown off - so...

Homework Statement Why Does A Nuclear Reactor Need A Body Of Water For Cooling? If steam is needed to run the generator turbine, why not send the water/steam exiting the turbine back into the reactor for additional heating without cooling the water/steam first? Homework Equations don't...

If a condenser were to lose its supply of cooling water and no trips were activated how could you calculate when the vacuum would be lost? i.e. calculate the length of time before no more steam could be accepted by the condenser.

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...

Homework Statement At 1:00PM, a thermometer reading 70oF is taken outside where the air temperature is -10oF. At 1:02PM, the reading is 26oF. At 1:05PM, the thermometer is taken back indoors, where the air is at 70oF. What is the temperature reading at 1:09PM? Homework Equations The Attempt at...