What is Cooling: Definition and 638 Discussions

a cup of coffee is heated to 100° then left in a room with a constant temperature of 68° after a minute the temperature of the coffee has dropped to 95° after another minute to 92 degrees. how much time must pass before the temperature of the coffee has dropped to 70°?

I'm on the lookout for a website dealing with calculation of cooling effects in deep freezers (for food storage and such). The main goal for me is to learn the basics of how to find the needed cooling effect from input values like amount of food, required temperature, room size, insulation, etc...

I understand that adiabatic cooling is the reason as to why, a valve releasing compressed air from a tire, would become cold. But I'm having a hard time grasping why this actually happens. I've been searching online, and I can't seem to find the type of simplified answer I'm looking for...

Homework Statement a) An object at 200 degrees F is put in a room at 60 degrees F.The temperature of the room decreases at the constant rate of 1 degree every 10 minutes. The body cools to 120 degrees F in 30 minutes. How long will it take for the body to cool to 90 degrees F? b) Show that...

Does't it seam odd that we have to use energy to cause something to loes energy. In a freezer you compress the gas (energy expended) to cool and de compress, so as to cool your fridge. Isn't there a way to cool somthing without useing energy (short of sending it to the antarctic).

All rocky planetoids are born as balls of molten magma, and take millions of years to cool, crust over, & solidify. As a rule-of-thumb, a planetoid's Cooling Time (tcool) scales as its Surface Gravity (g): t_{cool} \approx \frac{Heat}{Dissipation Rate} \approx \frac{Mass}{Surface Area}...

If a hot metal forging is cooled by dropping it into a pool of water, how many boundary/initial conditions do I need to solve for the temperature? I don't want to make any assumptions about temperature gradients within the forging itself (Biot number may be large, which precludes use of lumped...

Homework Statement This is the most confusing problem I have ever seen in my life. I just plain do not know what it's saying and what exactly a proportionality constant is. When you turn on an electric heater, such as "burner" on a stove, its temperature increases rapidly at first, then...

hey guys i'm thinking of building myself a pc next year and I've been reading a bit about water cooling. now every search i do tells me how great it is but the bit of me that spent 4yrs doing a mechanical engineering degree is a bit of a sceptic. firstly, sure, watercooling can deliver...

Perhaps this should be on the homework forum but I'm not sure, so I put it here. How do you calculate the cooling time scale of the surface of a white dwarf and the surface of the core of a white dwarf? I have an equation for the cooling scale of a white dwarf in general but I'm not sure how...

How does the laser cooling work? I have read that it is used to cool ions in vacuum, by absorbing their kinetic energy with a laser beam; but I don't understand why the laser cool the ions and not raise their energy by moment transfer

A cold beverage can be kep cold even on a warm day if it is slipped into a porous ceramic container that has been soaked in water. Assume that energy lost to evaporation matches the net energy gained via the radiation exchange through the top and side surfaces. The container and beverage have...

Homework Statement If you remove a glass of iced tea from the refrigerator, and leave it sitting on the table in a room with temperature 25 C, then Newton’s Law of Temperature Change gives the temperature of the tea after t minutes as f(t) = 25 − Ce−kt where C and k are constants...

Hi there I'm new to the forum, I stumbled across it while trying to find the answer to a question I have. I am currently building an autograss car and have come to the stage of trying to cool the engine which is a 2 stroke V6 outboard engine. Basically what I need to know is how to figure out...

Newtons cooling law? Homework Statement uh for my lab report the problem is i have to solve for the constnat and the lnC? look below Homework Equations teacher said something about LnT =Lne^-kt +LnC transposes into ==> LnT = -kt +LnC uh and i have the temperatures to do this.. but i...

So I have a slight problem since I'm getting a negative for time. A murder victim is discovered at midnight and the temperature of the body is recorded at 31C. One hour later, the temperature of the body is 29C. Assume that the surrounding air temperature remains constant at 21C. a)...

I have a circular stage (made of stainless steel) that rotates continuously. How can i cool it by conduction? I thought of using water cooled copper braids that contact the sides of the stage, but it'll cause a lot of wear since the stage will be rotating alot. Any suggestions on how i can go...

The problem is as follows, my friend and I want to make a fridge that uses cold air from outside, instead of an electrical compressor. We plan to simply use a fan, and pipe to bring cold air from outside into the fridge. So if our variables are: - Pipe length / Diameter - Fan speed /...

This is a 4 part ordinary differential equation problem. a.) You are a member of a CSI team that has discovered a dead body in a field. Upon discovery of the body you measure its temperature and find that it is 76.04058181\circF. 10 minutes later the temperature of the body is...

Homework Statement Adiabatic Steam turbine produces 4000 kW Steam is fed at 21 bar/475 deg C Exhaust is saturated steam (P=0.1bar) Exhaust is fed into condenser where it is cooled to 30 deg C Problem asks for flow rate of cooling water supplied to condensener if water enters at 15 deg C...

Problem From Newton's Law of Cooling, we can use the differential equation dT/dt= -k(T-Ts) where Ts is the surrounding temperature, k is a positive constant, and T is the temperature. Let \tau be the time at which the initial temperature difference T0-Ts has been reduced by half. Find...

To anyone familiar with the Ranque-Hilsch vortex tube: Say if the cooled air is allowed to pass over the vortex section of this tube, what would happen? Would the effect of cooling be the destruction of the vortex? or would it act to further decrease the temperature of the cold exhaust?

http://www.informaworld.com/smpp/content~content=a788582859~db=all G. V. CHILINGAR, L. F. KHILYUK, and O. G. SOROKHTIN, 2008, Cooling of Atmosphere Due to CO2 Emission, Energy Sources, Part A, 30:1–9, 2008 ISSN: 1556-7036 print/1556-7230 online DOI: 10.1080/15567030701568727 Heads...

I am going my coursework. My aim is to determine the specific heat of paraffin using the cooling method. I was wondering what would be the systematics errors?

http://www.sciencedaily.com/releases/2008/08/080801152137.htm ScienceDaily (Aug. 4, 2008) — Researchers in Germany, Switzerland, and the United States have shown, for the first time, that an extremely fast climate change occurred in Western Europe. This took place long before human-made...

Hi. I've searched through the forum and other internet resources and found several threads and sites, but haven't yet found any really detailed technical info. I'd like to build a series of cloud chambers. I'm an designer/researcher, with an interest in history and philosophy of science...

Hi, I was lying in bed unable to get back to sleep and I was thinking about something, remembered this forum, and thought I'd post it up here. Hopefully this topic is suitable for this forum. I installed a ceiling fan in my bedroom yesterday. Its a nice 44in Hunter fan and I'm pretty happy...

I wish to understand evaporative cooling. Apparently the principle consists in pumping the vapour above a bath, hence extracting it's most energetic corpuscles and achieving cooling. The aim is to derive the cooling power. My textbook states: \frac{dQ}{dt} = L\frac{dn}{dt} \propto p L...

Hey all. A question has come up regarding the rapid cooling of air, and if that cooled air is "denser" as result. On the surface, this seems trivial to me, but it quickly exceeded my ability to answer (not a physicist, just a hobbyist question asker and answerer at best). I've tried to draw...

Hi! I've really been wondering how air can possibly get cooled with a fan. I read somewhere on the internet that a fan creates a "draught" or a "draft." It seemed to imply that this somehow cooled the air, but I really don't know. I've heard, and it seems reasonable, that a fan just blows...

We were having tea with the family and my brother and I started wondering if holding the cup will help in cooling the tea. Lets say you have two identical cups filled with the same amount of the same temperature tea. You let one just sit and the other you grab with both hands . . . which...

Okay, so I've approached this problem from a number of different ways and have gotten some crazy answers. The poor student would be spending the day in a bath of ice if my answers were right :P Here's the problem : Trying to beat the heat of the last summer, a physics student went to the...

Hello everybody, my question is: do you get an increase in speed/power/performance when you "freeze" computer components such as the CPU with LN2 or phase change cooling, getting to under -100º,-150º. Because as long as I'm aware CPU´s are made out of semiconductors and as temp lowers the...

For Newton's cooling law q = h*a \Delta T q is the rate of energy loss of a body but for what unit time? For example if q = 3 does the body lose 3 watts of energy in 1 second?

Okay, I have been reading the article Laser Deceleration of an Atomic Beam by William D. Phillips see attachment. But I have a few problems: 1. Optical Pumping. On page 1, 2. column they write: I don't quite get the last part. How can the Zeeman effect change the selection rules? 2...

Homework Statement Consider an asteroid with an iron core \rho_m = 8000 kg\; m^{-3} covered by a thin silicate mantle \rho_m = 3500 kg\; m^{-3} with a thickness of 20% the raidus R of the asteroid. Assume that the internal temp is T_i = 600K and is constant throughout the core due to...

Shown in the attachment is a system consisting of a heat pump and other components. My question is how I can approximate the total cooling effect in Watts available to the cooling battery. I know that the ground water is about 5 degrees, and I have some other data as well, just shout as I'm not...

hi guys, i was hoping someone could possibly help me out with a problem i am having. please take a look at the attached picture. i am modeling a turbine blade, trying to find how different configurations for internal cooling configuration affect the overall temperature distribution in the...

When a liquid is cooled, the difference between the temperature of the liquid and the surrondings is measured. The results are: t(min) 10 20 30 40 T(°C) 60.7 36.8 22.3 13.5 Where t= time from the start of the cooling T= temperature difference Q(i) Process the above data...

Hi, Can anyone explain exactly why in field emission you get Nottingham heating? I can understand that you get joule/ resistive heating that makes sense. I can understand that you get cooling, the electron leaves the metal there is a loss of energy. But why does it matter if it is above...

Hi, I was wondering why a processor is producing more heat when you increase its clock frequency. My idea is that current is sent through the processor at the beginning of each clock cycle. This produces heat and after the current is gone (does it really disappear or is there always current...

Shown in the attachment is a system consisting of a heat pump and other components. My question is how I can approximate the total cooling effect in Watts available to the cooling battery. We know that the ground water is about 5 degrees, and I have some other data as well, just shout as I'm not...

I've got a project due this Friday whose objectives are no more than a single sentence: cooling tower improvements. This is for a thermal hydraulics class, so I thought I'd investigate the effects of different shapes of a hyperbolic cooling tower on heat flux q" through the walls of the tower...

http://motls.blogspot.com/2007/01/peer-reviewed-global-cooling.html Just for a change. <Edit by Moonbear: Here is a direct link to the article being discussed in the blog http://www.springerlink.com/content/g28u12g2617j5021/?p=77874d861902420aacca82524790dc89&pi=7 All discussion within the...

Homework Statement A solar hot-water-heating system consists of a hot water tank and a solar panel. The tank is well insulated and has a time constant of 64 hr. The solar panel generates 2000 Btu/hr during the day, and the tank has a heat capacity of 2 degrees F per thousand Btu. If the...

I'm trying to understand the concept of free cooling. I've found that this is the production of chilled water without the use of chillers, i.e. the use of cool air. But what I don't get is that if the temperature outside is low, isn't the need for cooling pretty much not there? I only see this...

Homework Statement A small object of unknown temperature was placed in a large room that had the fixed temperature 30 degrees C. After 10 minutes, the object's temperature is -10 degrees C, and after an additional 10 minutes, the object's temperature was -5 degrees C. What was the initial...

Consider an asteroid with an iron core (pc = 8000kg/m^3) covered by a thin silicate mantle (pm = 3400kg/m^3) with a thickness of 20% of the radius R of the asteroid. Assume that the internal temperature Ti = 600K is constant throughout the core. The thermal energy of the core is 3*k*Ti per...

Homework Statement The equation dQ/dt = k ( T - Troom) is Newtons law of cooling. dQ/dT being the rate of heat loss. I want to convert this equation to dT/dt, the rate of temperature decay. How do i go about doing this? Homework Equations The Attempt at a Solution Is Q...

What caused the universe, specifically the Earth, to cool after the big bang? Was it because of the space expansion and thus the relationship between wavelength and energy (as wavelength increases E drops?) or what? A basic answer is good =] Thanks.