Calculate time to reach temperature

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Login or Sign Up. Temperature Time to Rise Calculator. Posts Latest Activity. Page of 2. Filtered by:. Previous 1 2 template Next.

Oven Builders: I've created an excel spreadsheet that will calculate the time it will take for the oven you are building to reach a desired temperature. All you do is enter the internal oven dimensions, the starting room temperature, the desired curing temperature and the total element wattage into the yellow boxes. The spreadsheet will then display the time to reach that temperature in the green box. It also displays how many amps an oven of that wattage will draw.

This calculator is based on an oven built with metal interior and exterior walls and 2" of mineral wool insulation. This should help everone to have realistic expectations on how quickly their oven will reach working temperature.

Tags: None. My input values come up pretty close to how long it takes mine to reach the desired temperature.

Calculating time for object to reach ambient temperature in an oven

I have two suggestions: 1 Make a legend so people know to only put data into the yellow fields. Even though it is protected 2 Make it possible to change insulation thickness. I think it should be a sticky for sure though. Thanks for putting the effort out to come up with this spreadsheet. Wish it was here a couple of days ago when I was started a thread on warm up temps.

Comment Post Cancel. Fortunately I'm using Mineral Wool Insulation. Who says you can't teach an ole dog new tricks? I will look for it. As for the insulation, the amount and type you use will change the time slightly but as long as you are using some kind of insulation of appreciable thickness it's not going to have nearly the effect on the calculation that oven volume and wattage will have.

In order for me to modify the program to account for insulation thickness, I'm going to need some real world data from you fine folks. If anyone has an oven, a temperature gauge and a stopwatch and is willing to provide feedback on how many minutes and seconds it took them to go from temp A to temp B along with the type and quantity of insulation they are using, I will be able to modify the program to account for different insulation.

Re: Temperature Time to Rise Calculator just wanted to say thanks for spending the time on this, its probly trivial with the temp controller ill be using, but it gives me a head up on what to expect.

Also great for a future project i was thinking about I'll have to compare with my oven. I have 10" fiberglass walls, but HardiBacker for internal walls. Havn't got all me elements in yet, 2 had to be special ordered.Hot Threads. Featured Threads. Log in Register. Search titles only. Search Advanced search…. Log in. Forums Engineering General Engineering.

calculate time to reach temperature

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Calculating time for object to reach ambient temperature in an oven. Thread starter graeme89 Start date Sep 19, Hi all, I am currently doing an engineering internship still an undergradmy field is electrical engineering so thermodynamics just confuses me! My job has been to come up with a good Environmental Stress Screening porgram ESS plan, while doing this I have realised that the industrial oven that this company has is, well, crap.

I am not the only one to realise this and the wheels are moving on getting a new oven, although I need to highlight how bad the current oven is for the head dudes to give the green light. Right, to the actual problem. I am trying to figure how long it should theoretically take for the rack of components in the oven to reach the desired temperature.

There will be practical tests for this but I could do with the theory to back me up. The plan is to set the oven to 80C and C and see how long it takes for the equipment to reach its steady state, now all the equipment is going to be running so getting it to it's hot steady state shouldn't be as hard as getting it to it's cold steady state. From what I can gather from the internet I am basically looking at estimating the thermal time constant of the system. The surface area I am not so sure about because of what surface to take as the 'area' the dimensions being mmXmmXmmand the heat transfer coefficient I a have no idea how to calculate.

I am assuming that the heat transfer coefficient is different for every oven? The power of the current oven is 3kw and the new oven is 51kw.

I am guessing the power of the oven has to impact the transfer coefficient in some way because if it didn't then the time constant would be the same for both the garbagety oven and the new hence no point getting a new oven.Once you have calculated the thermal power used to heat the water, as represented by Pt in the above equation, divide this number by the heater element rating to find out how long it would take to heat your water.

Pt is the power used to heat the water, in kWh. L is the number of liters of water that is being heated and T is the difference in temperature from what you started with, listed in degrees Celsius. Substitute in the appropriate numbers into the equation. So imagine you are heating 20 liters of water from 20 degrees to degrees.

Calculate the amount of time it takes to heat the water by dividing the power used to heat the water, which was determined to be 1. So if your heater element rating was 3. Therefore, it would take 0. Elyse James began writing professionally in after deciding to pursue a career in journalism. She has written for "The Algonquin Times" as a general assignment reporter and published blogs and articles on Webcitybeat.

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Close this window and log in. Are you an Engineering professional? Join Eng-Tips Forums! Join Us! By joining you are opting in to receive e-mail. Promoting, selling, recruiting, coursework and thesis posting is forbidden. Students Click Here. Related Projects. Is the following logic correct to estimate the time required for a metal object in an oven convection to be heated up to ambient temperature?

calculate time to reach temperature

Dividing power P into energy W gives me the time required to raise the object's temperature uniform to the oven temperature. I just need a reasonable estimate to ensure that the entire object is heated to the ambient temperature; overshooting is acceptable in this case. Only if you're assuming that the only means of losing heat is by radiation, which, for terrestrial applications, is usually a bad assumption, particularly if your statement that it's a convection oven is correct.

Additionally, I don't see an emissivity term in your radiation expression, and it's highly unlikely that a typical metal object would be a perfect blackbody. In general, radiative transfer is two-way, not one, so you need to have an expression for the emission of the object.

Since it's supposed to be in a convection oven, then you need to have a forced convection heat transfer expression to account for that. And, depending on the object's thermal conductivity, you may need to constrain the equations to ensure that you don't grossly underestimate the time. You've to perform a transient analysis. Look for lumped capacitance approach. Thanks for your helpful recommendations.

Is it reasonable to just consider the radiative heat transfer when a I wish to obtain a conservative time estimate and b the oven has highly reflective aluminum walls and ceiling? Not necessarily, it may just mean that you have to consider a multilayer lumped model, rather than a single RC-type.

Actually, the converse would be true.

calculate time to reach temperature

Highly reflective surfaces have lower emissivities, potentially making convection more dominant. Otherwise, your basic concept is roughly correct. IRstuff: Thanks for your correction. Based on what you just shared, is my logic now correct for steady-state conditions? Using the values below, I appear to be missing a critical element since the calculated result is negative.

Can anyone help?By using our site, you acknowledge that you have read and understand our Cookie PolicyPrivacy Policyand our Terms of Service. Physics Stack Exchange is a question and answer site for active researchers, academics and students of physics. It only takes a minute to sign up. I work at a bakery. We have certain products that have to be put in the refrigerator for x number of hours before we can use them. The cakes we use for cakeballs have to refrigerate for 12 hours, apparently But no one has calculated this to know whether or not that's true.

They're just guessing. I don't think it will take 12 hours for our sheet pans to reach 49 degrees Fahrenheit the temp of the fridgebut I have been out of school for a while and am pretty rusty on my formulas. I was wondering if someone could help me with the formula. I honestly would like to do the math myself, so a simple formula is all I ask for. I hope someone can help me solve this!

This method assumes the temperature of the cooling object is uniform no internal temperature gradients. In that case we can use Newton's cooling law to calculate the heat loss rate leaving the object as:.

This is a first order, linear DE which solves with separation of variables. There are two main difficulties with this calculation:. For larger objects the assumption of thermal uniformity may no longer be valid, as the outer layer of the object will reach higher temperatures earlier.

In that case we need to take internal transient heat conduction into account, which is mathematically much more demanding. For those reasons, constructing experimentally determined cooling curves may be far more practical and accurate. Sign up to join this community. The best answers are voted up and rise to the top. Home Questions Tags Users Unanswered. How to calculate the time it will take for a specific object to reach a certain temperature?

Ask Question. Asked 3 years, 2 months ago. Active 1 year, 1 month ago. Viewed 10k times. Brenna Brenna 31 1 1 silver badge 2 2 bronze badges. It would make more sense to take an experimental approach: just measure the temperature of the cakes every 1 hour, say, for a 12 hour period.

And then plot it versus time. Keep in mind that there may be legal requirements to observe as well. Active Oldest Votes. There are two main difficulties with this calculation: 1. Internal temperature gradients: For larger objects the assumption of thermal uniformity may no longer be valid, as the outer layer of the object will reach higher temperatures earlier. Gert Gert Sign up or log in Sign up using Google.The time taken t to heat the object when energy is supplied at power P is given by:.

The formula for the amount of heat energy required to produce a certain change in temperature is:. First, calculate the change in temperature using the formula:. Every material has a unique specific heat capacity, which tells you how much energy it takes to heat it up by 1 degree Kelvin or 1 degree Celsiusfor a specific amount of a substance or material.

Choose the appropriate value for your substance. The final quantity in the equation is m for the mass of the object. In short, it takes more energy to heat a larger amount of a material.

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The formula states:. So it takes Note that it requires less energy to heat ten times as much lead by the same amount, because lead is easier to heat than water.

Power measures the energy delivered per second, and this enables you to calculate the time taken to heat the object in question. Time taken t is given by:. Where Q is the heat energy calculated in the previous step and P is the power in watts W, i. Imagine the water from the example is being heated by a 2-kW 2, W kettle.

The result from the previous section gives:. So it takes just less than 84 seconds to heat 1 kg of water by 40 K using a 2-kW kettle. If power was supplied to the kg block of lead at the same rate, the heating would take:. Again, this reflects the fact that lead heats up more easily than water.

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