# Questions tagged [temperature]

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### Why does moving air feel cold?

I'm taking a thermodynamics class and had the following question. I was going to ask my professor directly, but it seems like a stupid question with a simple answer, so I thought I'd try my luck here ...
• 131
25k views

### Affixing a thermocouple to a surface

I'm looking for advice on how to attach a thermocouple to a metal surface in a fashion that's relatively temperature resistant (more-so than) glue. I've got some very fine gauge wire on hand to make ...
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### How does a microbolometer (IR camera) work?

I am currently doing a project which has led me to my first encounter with IR cameras, and I am therefore quite curious as to how they operate. Specifically, I would like to know the following How is ...
• 273
646 views

### How do I compute the force required to pierce HDPE?

I have a $2\text{ mm}$ sheet of HDPE at $280-320^{\circ}\text{ F}$. I want to pierce the skin of this sheet with a $2\text{ mm}$-high pin with a surface area of $3.33\text{ mm}^2$. The pin is also ...
• 353
2k views

### Steel expanding in a tight space

Hypothetical question: What would happen if I were to cool down a steel cylinder to make it contract, and then slide it all the way into a cylindrical hole in a room-temperature solid steel box? The ...
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12k views

### How do train tracks handle really cold weather?

First of all, I'm interested in train track only, not the rolling stock. How are tracks built to cope with really cold weather? An example might be some place in Canada or Siberia. Ice would ...
• 507
5k views

### How can I calculate the temperature rise of a circuit board for a given power dissipation and area?

I have a PCB of approximately 4" x 4". It has a single long spiraling trace on it. The trace is 50 mil 4 oz copper, so nominally it's good for something like twenty amps before it overheats. But this ...
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283 views

### Having three heaters on single PCB

I posted this question on electronics SE, but was suggested that I post it here. I basically having three heaters (serpentine pattern) on a PCB (fiberglass board), as the following image shows: The ...
3k views

### O-Ring vs flat washer for air seal

I'm interested in whether a flat rubber washer or equivalent is good enough to replace an o-ring in a low pressure application (edit: I meant low pressure differential. My bad.). The reason is that ...
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693 views

### Baffle vs Bottom Temperature Measurement/Control

In an industrial jacketed reactor, we have two temperature probes: one on a baffle the extends down about to the 50% fill line one built into reactor, very close to the bottom valve. When is it ...
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4k views

### How do I determine the thermal resistance of a metal box?

Suppose I have a sealed enclosure, say this one from Hoffman: The box is 16"x12"x6", made of galvanized steel with a wall thickness of .0635" or .0785" (gauge 16 or 14). I'm planning to put some ...
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587 views

### At which temperature and humidity should outside air be drawn inside?

I have a greenhouse that get’s mold in the winter because it’s to humid. I have now installed a heater and a ventilation system drawing outside air into the greenhouse. I wish to start the vent based ...
• 143
77 views

### Easily compute a good approximation of heat conductivity of cooled semi-vacuum (water vapor + air)

I am preparing a classroom demonstration about heat, including a demo of how a satellite loses heat only radiatively, since it's flying through a vacuum. I'd like to make the vacuum-production ...
464 views

### Can a chain of nested thermal heat pumps be used to to gain thermal energy out of the environment?

Assume the following setup: ...
228 views

### Prolong frozen ground conditions (to trick fruit trees into flowering later)

There is a common problem with fruit trees in temperate climates where the trees flower before the last frost. Generally speaking, if the tree has flowered, and the temperature drops below freezing, ...
• 399
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### Got to pour outdoor concrete next week, but forecast is cold. What are my options?

I have to pour outdoor concrete next week. The pour is in two main parts - a 100 mm cover / 2nd pour over a 6 x 3 m area of existing concrete from a 1st rough pour, and the bottom ...
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486 views

### How to extract a building's heat isolation and thermal inertia based on temperature curves?

So imagine we have a house with some isolation and some thermal inertia. This house also has a heating system that turns on (starts heating) when the observed temperature curve goes below some ...
138 views

### Should the temperature of a heated metal cone decrease in a plastic enclosure?

Summary A steel cone is heated by a nichrome ribbon to 45–50 °C. I placed a Type K thermocouple over the surface of the metal to measure the heat transferred over the metal surface. The thermocouple ...
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190 views

### Controlling the temperature with high precision

I need to control the temperature with high precision, and for this task would be good a temperature controller with pt-100 sensor, something like this one PID Temperature Controller ITC-100. As I see ...
• 143
261 views

### How to deal with thermal expansion in a city wide heating system?

How to deal with thermal expansion in a city wide heating system? Background: As part of the program to combat pollution in and around Beijing, my adopted city of Zhuozhou (population, over half ...
109 views

### Analog PID controller - settings wrt $V_{err}$ - setpoint always higher than room temp

I designed from scratch an analog PID controller to mantain a temperature selected in the range of 60 to 80ºC with a room temp say = 20ºC. The "plant" is a simple 4R7 5 W resistor heated by a PWM-...
823 views

### What does "+- %/K" mean?

On a datasheet, sensitivity temperature drift (TCs) is specified in %/K. I read this as "the percent change per kelvin". Is this is simple as this sounds, or is there a reason for using kelvin over ...
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### Store seeds at 1°C

I have prunus pits that I stratify in a refrigerator during winter. Normally, the seeds germinate in springtime, which is ideal. However, often some of the seeds germinate prematurely. When this ...
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### Why do heating elements have lower rated temperatures in vacuums?

I have noticed when examining performance of various heating elements in different atmospheres that in a vacuum maximum temperatures are lower than the in air temperatures. Why is this? (Typical ...
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### Would creep have been a major problem for pykrete designs?

During world war two the British had plans for an aircraft carrier made of pykrete (a mixture of 14% sawdust or wood pulp and 86% ice.) the idea was to have a refrigeration system to stop the ice from ...
• 131
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### Saturation Temperature of Binary Mixture

I have a binary mixture of water and methane. The system is at 2000kPa and I am trying to find the saturation temperature of the water in the mixture. I know Tsat is a function of partial pressure, ...
459 views

### Hack a kitchen freezer for lower temperature

Common home freezers usually have the lowest temperatures of about -24 degrees Celsius. Freezers that go lower exist but these are much more expensive (times much). I wonder whether a common kitchen ...
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### How would you seal a hole in an HDPE container that's in -20C environment

I have a temperature sensor in a -20C freezer. The probe is going into a bottle filled with propylene glycol solution. I want to seal the hole where the probe is inserted into the bottle. What's a ...
• 123
155 views

### High Fan Speed Not Cooling As Expected (PWM, Arduino)

We have a system involving a fan blowing air through a box which contains a small (but constant) heat source and a temperature sensor. The fan speed is controlled with PWM. As PWM (and hence fan speed)...
93 views

### How can I trust a K-type thermocouple purchased from a no-name company?

I am doing some temperature measurements for reliability testing, over an expected range of 16C to 45C. I have an NIST traceable thermocouple thermometer (S220-T8), however it does not come with ...
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741 views

### How can we control the output temperature of a multi-input single-output pipe air-flow system?

I am trying to optimize the heat control of a test bench at our facility. The test bench is basically a pipe with an air flow that can be heated up to desired temperature. To heat the air flow up, ...
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### How to calibrate an oven thermometer?

Is there a DIY method for calibrating thermometers in the 200 to 250 degree Celsius range? In a moment of boredom I decided to put all five of my wife's oven thermometers side-by-side in the oven and ...
275 views

### PV Diagram Pressure temperature volume increasing what is net effect on output?

I am not properly understanding this question. please help! Most of the process on PV diagram have this kind of curvature But in the question above, its bit weird. My thoughts: Pressure, temperature ...
369 views

### How you calculate the temperature scaling factor?

Used to obtain the corresponding pressure at ambient temperature. Example when testing Proof or burst pressure to a given value at 300°F, but you will test with corresponding pressure (higher) to ...
140 views

### How to calculate adiabatic air temperature loss caused by increase of humidity?

I'm searching for an approach on how to calculate the adiabatic temperature loss of air when increasing its humidity by a humidifier. Assumed we have the following setup: Air measuring position 1 (...
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652 views

### Is a Home's Temperature Affected by Solar Gain Through Windows on Cloudy Days?

Do homes increase in temperature due to solar gain with curtains open if it's overcast? In other words, Does having curtains closed reduce the temperature of the home on an overcast day? In other ...
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89 views

### Is it necessary to consider temperature effect on waling?

Many text book literature on braced excavation mention the necessity to consider additional load due to temperature effect on struts. But nothing is mentioned about waling. Why is this so? Wouldn't ...
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### How to measure a bearing temperature in a pump?

I found that Resistance Temperature Detectors (RTD) are mostly used for bearings, but it's not easy to drill the casing and we need to take a signal out to PLC and LabVIEW. Is there a sensor that can ...
2k views

### Calculating the Fraction of Steam in a Mixture

I have a stream ($10,000$ $m^3/d$) of inert gas and steam. The temperature of the stream is $195$ $^oC$, and the absolute pressure is $1455$ $kPa$. I am trying to find the amount of steam that can ...
67 views

### What standards or industry guidance define a top temperature for human contact to surfaces?

I'm looking for guidance to define how hot is too hot when related to human safety. I have heard of a general limit from OSAH of 60 °C (140 °F) being ok for contact up to 5 sec. Are there better ...
419 views

### I want to dissipate 3 kW of heat with an air conditioner. How big of an air conditioner do I need?

So the title says it all. I have a room (4 m x 4 m x 2.5 m) which is closed.(Actually there is a window and I could add a 50 cm panel fan if needed as an exhaust if that will help.) I have some ...
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### Lowest temperature at which a spring powered mechanical wrist or pocket watch will stop operating

In the Wired article 9 Russian Adventurers Mysteriously Froze to Death. A New Theory Explains Why, it is stated that: Without body heat to keep it warm, in such cold weather—estimated to be –13 ...
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### What happens when pumps are blocked off?

What will be the result if the pipe losses is greater than head produced by the pump? What will be the result if outlet is closed?
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### What's the difference between aircon modes Auto, Sun, Snowflake?

Most air conditioners have three modes: Auto, Sun, Snowflake What is the difference it terms how it works?
1 vote
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### Up to what temperature, can titanium be safely used?

I was thinking about the realization of a pottery oven, and I wondered which material I could to make the inner walls. Most often the inner walls seem to be made of some kind of hard mineral wool. I ...
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### What's the thermal bounds of a typical computer case fan?

I'm thinking of repurposing computer fans (case fans and/or CPU/GPU fans) for a hobby steam turbine project. So the idea would be to use the fan rotors in the turbine to drive the shaft (discarding ...
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### How do I determine the temperature inside a transformer vault?

I am trying to determine the temperature of an underground concrete vault buried 10m underground. The vault has the following dimensions: 2640mm x 5995mm x 2640mm with a wall thickness of 250mm. The ...
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### How large of an area of the earth's surface would we need to cover in mirrors to negate global warming?

How large of an area of the earth's surface would we need to cover in mirrors to negate current levels of global warming? Let's assume that the reflective component of the mirror is made of aluminium ...
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