Heat loss Definition and 147 Threads

I am working on an incubator/shaker for laboratory use. I am trying to work out a temperature failure and repair it, but that is besides the point here. I was looking through the user manual to try to get some clues about the failure and I came across this: "Depending on various conditions...

I'm trying to size (in watts) a heater to heat a glass of water from ambient (Ti) to a certain temperature (Tf) in a given time period (say, 1 hour). The heat-loss from the glass at Ti is 0 watts. The heat-loss from the glass at Tf is Y watts. I'm assuming that the heat loss increases...

I want to build a small geothermal cooling unit to cool one small room in my house. If i lay 0.5" pex pipe which is 0.475" ID. The big question is how long does the water flowing in the pex tubing have to stay under ground. Constant ground temperature is about 55 degrees F around my house. I...

Homework Statement Alright so I am doing a fairly simple experiment testing how the temperature of water in a beaker effects how fast heat is lost. Have done the tests, but need to get some predicted results to compare them too. Have been using a glass beaker filled with 200ml of water...

Homework Statement I'm not sure if this problem should go here.. it's a bit of math and a bit of physics. I know that the concepts should be simple but I don't really know where to start.. Here's the question: a) Determine the breakeven point for heating oil in dollars per gallon – the point...

Hello, I'm engineering a heat-pump for my senior project. My professor is out of town and these questions have been on my mind. I'm trying to calculate ACTUAL heat loss through the tent walls and ceiling. I'm using a tent 10ft x 5ft x 6ft. I'm trying to heat it with approx. 750 btus/hr...

Feet first... How do I calculate heat loss by evaporation from the surface of a swimming pool, at a range of temperatures and given a range of conditions? Any help gratefully received! Nick

Homework Statement A man of 75 kg (1.77 m^2 surface area) in weight, dressed in appropriate winter clothing stands on a winter pond. The temperature outside is -5 degrees Celsius. Assume that the surface layer of his skin is 5 mm thicker and is not perfused with blood (behaves as an insulating...

I’m an entrepreneur in South Africa with the rights to a type of insulating coating. It’s new on the market here and no real research and development has been done on the coating to determine how much energy it can save. I’m a marketer and I don’t have the educational background to answer this...

Homework Statement If the specific heat capacity of water from an experiment is smaller than its actual value, does it mean more heat is lost to the surroundings? If the heat is emitted by a wire into a cup of water and the change in temperature is measured, does it mean that the change in...

Homework Statement We are heating up the cabin log with a furnace that has strength of 4 kW. The surface of the walls of the log cabin is 35 m². What is the temperature in the log cabin, if the outside temperature is -20 °C? The thermal conductivity of wood is 0.4 W/mK; the average wall...

I have a large circular tank made of concrete that has a volume of 9,300,000 litres. The diameter of the tank is 48.7 meters. The side wall of the tank has a height of 4.57 meters. The tank is set into the ground by 3.57 meters and 1 meter of the tank protrudes from the ground. The tanks'...

Homework Statement If 10 kilogram of ice at zero degrees celsius is added to 20 kilogram of steam at 100 degrees celsius, what is the temperature of the resulting mixture?Homework Equations uhm... perhaps how many solutions are required to arrive at the answer?The Attempt at a Solution I and...

I have a heat transfer question, I work in a plant and am doing a re-insulation project. If an unexposed steel steam pipe (k=47) of diameter 10 inches, maintains an internal temperature of 460F and is exposed to ambient air (70F) flowing at 5 mph across the pipe. Determine the heat loss per unit...

Homework Statement If only conductive heat loss was significant for a house, then by what percentage would you lower the heat loss if the temperature was reduced inside from 73°F to 67°F, when the outside temperature is 21°F? (Hint: Try using a ratio.) Homework Equations Unknown The...

Homework Statement A thermos consists of two layers (see fig). The core contains a liquid with temperature T_1. The outer layer contains air at low pressure with temperature T_2. The surrounding air has temperature T_3. At t=0, T_2=T_3. Assume that T_3 does not change with time, and that...

Heat loss from an insulated water tank ----- Thermodynamics Hi and thanks in advance for any help with this problem. If I have a very very well insulated tank of water of say 4 litres. If we could assume that the tank had no heat loss... The tank is heated by an electrical device that...

I understand that double glazing reduces heat loss by minimising conduction of heat from the interior pane to the exterior one. Air is a very bad conductor so the heat does not travel from 1 pane the other very easily. Is that correct? If so, why doesn't all the heat just build up in the space...

Homework Statement A metal (doesn't say what metal) is in a heater that is set to 700 K. If the temperature of the ball is 900 K then the rate of heat loss = 0.10 J/min. What is the rate of heat loss when the ball's temperature = 800 K. The ball's emissivity doesn't change appreciably with...

Homework Statement Which one of the following statements about heat flow is FALSE? (A) Thermal conduction is due to energy exchange during collisions of atoms or molecules. (B) Thermal convection occurs only in fluids. (C) The rate of heat flow due to thermal radiation is proportional to the...

All the info I could obtain talks about heat loss through windows and doors. I am trying to get several store owners in my town to close there doors in the middle of winter and summer. The average door is 28 sq ft. I am assuming the inside temperature is 68 degrees and the outside temperate...

Homework Statement A stack of identical coins is all at a temperature of 100 C. The coins are transferred to a container of room temperature water. After thermal equilibrium is reached the final temperature is 35 C. The Heat lost by a single coin is less/greater/equal to the heat lost by all...

How can I calculate the heat loss from the surface area of a box into air? Also, how can I calculate the heat/energy loss from a heated gas (into ambient air)?. Thanks in advance.

Hello, How can I determine the heat loss (to air) from a box of a specific material, with a heat source inside of it? Also, how do you calculate the heat/energy loss of a heated gas into ambient air. Thanks

Homework Statement Solve the heat equation: u_{t} = u_{xx} - u - x*e^{-t} BC: u(0,t) = 0, u(1,t) = 0 IC: u(x,0) = x Homework Equations The Attempt at a Solution The only progress I've made so far is figuring out that the steady state solution is zero. Other than that I don't...

Homework Statement A rectangular building is being designed to minimize heat loss. The east and west walls lose heat at a rate of 10 units/m^2 per day, the north and south walls at a rate of 8 units/m^2 per day, the floor at a rate of 1 unit/m^2 per day, and the roof at a rate of 5 units/m^2...

Homework Statement In this problem you will estimate the heat lost by a typical house, assuming that the temperature inside is T_in= 20degrees C and the temperature outside is T_out = 0degrees C. The walls and uppermost ceiling of a typical house are supported by 2 x 6-inch wooden beams...

Strangely, this is for a Mat Sci Class. It is probably not as complicated as I am making it out to be, but the book has no suggestions on how to handle this problem. Homework Statement Calculate rate of heat loss through a fireclay refractory wall of wall with thickness .1m. Furnace...

I have some extended aluminum part which is at low temperatures. It is connected by a thin alu rod to a cooling device held at a constant temperature. How can I estimate the rate of cooling through this thin rod given the material specific constants? I assume the heat exchange with the...

I have an open water pond which will be receiving hot water (75oC) at a continuous steady rate. I want to know the temperature of the water leaving the pond at the other end. Is there a formula I can use to calculate this from the following information? Volume of pond (1650m3) (25mx25mx2m...

1. The problem statement: A 5.00 x 10^2 kg object is attached by a rope through a pulley to a paddle-wheel shaft that is placed in a well-insulated tank holding 25.0 kg of water. The object is allowed to fall, causing the paddle wheel to rotate, churining the water. If the object falls a...

What percentage of electrical energy is lost as heat by the transformer that supplies a house with 240V ac?

Hi all I found values for heat transfer from a pool on the following website: http://www.engineeringtoolbox.com/heat-loss-open-water-tanks-d_286.html can someone please tell me how reliable is this information? especially that they didn't mention free natural convection, or is it...

What is the most practical method of measuring where a home is losing heat? The idea is that these measurements would be the first step in calculating the most cost-effective improvement, deciding whether to increase insulation in ceiling, walls or floor, to upgrade to double glazed windows...

Homework Statement assuming that the temperature inside is T_in = 20 C and the temperature outside is T_out = 0 C. The walls and uppermost ceiling of a typical house are supported by 2*6-inch wooden beams (k_wood = 0.12 W/m /K) with fiberglass insulation (k_ins = 0.04 W/m /K) in between. The...

Sir, A man covers his body with a blanket of thickness 4 mm. His temperature is 37 degree Celsius and that of the atmosphere is 27 degree Celsius. If the coefficient of thermal conductivity of wool is 1.2 x 10^(-5) W/m.K , what is the heat lost per hour per square meter area? I solved it...

This was a question posed to me by a homeowner. I don't know very much thermodynamics and hope someone here might have a better understanding. They have a run of 3/8in copper pipe leading from their water heater to various taps. On cold mornings, it takes a long time, for hot water to flow to...

A room is 5x5x5=125 m3 and holds a temp of 30C. On the other side of all the walls the air is 20C. I measure that the room temperature drops about 0.001C per second. If I now use this equation... \dot Q = V \cdot C_P \cdot \rho \cdot \dot T ...I get the amount of heat that needs to...

A copper sphere of 8cm diameter is blackened and suspended from the ceiling by a fine thread in a room kept at 25 degrees C. The sphere is then heated to a temp of 147 degrees C. Calculate the net rate of heat loss by the sphere. Im not given any constants such as stefans or the emissivity...

Help! Heat Loss! A cup of coffee (with a lid) is enclosed in an insulated cup 0.5cm thick in the shape of a cube 13.1cm on a side. The thermal conductivity of the cup is 0.0002 cal/s*cm*DegreeC. The temperature of the coffee is 87C and the temperature of the surroundings is 14C. Find the...

the incredible lifting machine heat loss?? While stumbling upon this website on the Incredible lifting machine, http://tigre.ucr.edu/dipen/phy11/heat.htm I was wondering what could be some of the reasons why the work down calculated as in mgh does not equal to the work done under the pv...

This is actually pretty embarrassing for me but a question just popped in my head today and in my three years of studying Engineering Physics nobody gave me the answer: Why is it that heat effects are always considered as energy loss? Really. I understand that's not really convenient if...

Suppose a man is losing heat at a rate of 300 W. His body temperature is 1.5 deg C below normal, and he begins to shiver. If his mass is 65 kg, how many hours will it take for his temperature to rise to normal? Correct answer: 0.75 hrs General feedback: First determine how much energy is...

Hi everyone! I have some questions... 1. Describe the fall in the temperature of a cooling substance as a function of time. 2. Describe the effect of temperature gradient upon the rate of temp. fall. 3. Describe the effect of the nature of the substance upon the rate of fall...

Hello again... 1. Some claim that the freezer makes ice faster if one pours boiling water instead of cold water on the ice trays. Is this true? How come? 2. If one intend to drink a coffee soon, he has to stir it with teaspoon. How does that help? 3. How does a thermos bottle keep...

Hello everyone. I have questions to ask. 1. What is Newton's Law of cooling? 2. The factors that affect the rate of cooling of a body are nature of a substance and temp. gradient. What are those? 3. How does each affect the cooling of a body? Are each of them varies...

Hello all. I have not studied any thermodynamics, and very little physics. One unit of mechanics and one unit of wave mechanics so far. I was wondering about laptop computer cases. Some now are titanium, some still plastic. Is titanium better for absorbing and radiating out the heat? Ie...