Heat flux sensor Totally Explained

Everything about Heat Flux Sensor totally explained

A heat flux sensor is a commonly used name for a transducer generating a signal that's proportional to the local heat flux. This heat flux can have different origins; in principle convective-, radiative- as well as conductive heat can be measured. Heat flux sensors are known under different names, such as heat flux transducers, heat flux gauges, heat flux plates. In addition there are several instruments that actually are single-purpose heat flux sensors like pyranometers (for solar radiation measurement) and Schmidt Boelter gauges (for measurement of heat flux from fire). In SI units heat flux is measured in Watts per square meter.

Usage

Heat flux sensors are used for a variety of applications. Common applications are studies of building envelope thermal resistance, studies of the effect of fire and flames or laser power measurements. More exotic applications include estimation of fouling on boiler surfaces, temperature measurement of moving foil material, etc.
The total heat flux is composed of a conductive, convective and radiative part. Depending on the application, one might want to measure all three of these quantities or single one out. An example of measurement of conductive heat flux is a heat flux plate incorporated into a wall.
   An example of measurement of radiative heat flux is a pyranometer for measurement of solar radiation.
   An example of a sensor sensitive to radiative as well as convective heat flux is a Gardon or Schmidt Boelter gauge, used for studies of fire and flames.
   There are various examples of sensors that internally use heat flux sensors examples are laser power meters, pyranometers etc.
   We will discuss three large fields of application in what follows.

Applications in meteorology and agriculture

Soil heat flux is a most important parameter in agro-meteorological studies, since it allows one to study the amount of energy stored in the soil as a function of time.
Typically two or three sensors are buried in the ground around a meteorological station at a depth of around 4 cm below the surface. The problems that are encountered in soil are threefold: ť First is the fact that the thermal properties of the soil are constantly changing by absorption and subsequent evaporation of water.

Secondly the flow of water through the soil also represents a flow of energy, going together with a thermal shock, which often is misinterpreted by conventional sensors. ť The third aspect of soil is that by the constant process of wetting and drying and by the animals living on the soil, the quality of the contact between sensor and soil isn't known.

The result of all this is the quality of the data in soil heat flux measurement isn't under control; the measurement of soil heat flux is considered to be extremely difficult.

Applications in building physics

In a world ever more concerned with saving energy, studying the thermal properties of our buildings has become a growing field of interest. One of the starting points in these studies is the mounting of heat flux sensors on walls in existing buildings or structures built especially for this type of research.
The measurement of heat flux in walls is comparable to that in soil in many respects. Two major differences however are the fact that the thermal properties of a wall generally don't change and that it isn't always possible to insert the heat flux sensor in the wall, so that it has to be mounted on top of the wall. When the heat flux sensor has to be mounted on top of the wall, one has to take care that the added thermal resistance isn't too large. Also the spectral properties should be matching those of the wall as closely as possible. If the sensor is exposed to solar radiation, this is especially important. In this case one should consider painting the sensor in the same color as the wall. Also in walls the use of self-calibrating heat flux sensors should be considered.

Applications in medical studies

The measurement of the heat exchange of human beings is of importance for medical studies, and when designing clothing, immersion suits and sleeping bags.
A difficulty during this measurement is that the human skin isn't particularly suitable for the mounting of heat flux sensors. Also the sensor has to be thin: the skin essentially is a constant temperature heat sink, so added thermal resistance has to be avoided. Another problem is that test persons might be moving. The contact between the test person and the sensor can be lost. For this reason, whenever a high level of quality assurance of the measurement is required, it can be recommended to use a self-calibrating sensor.

Properties

A Heat Flux Sensor should measure the local heat flux in one direction. The result is expressed in Watts per square metre. The calculation is done according to:

phi_q =frac

is the sensor response time, the reaction to this is:
Further Information

Get more info on 'Heat Flux Sensor'.

External Link Exchanges

Do you know how hard it is to get a link from a large encyclopaedia? Well we're different and will prove it. To get a link from us just add the following HTML to your site on a relevant page:

<a href="http://heat_flux_sensor.totallyexplained.com">Heat flux sensor Totally Explained</a>

Then simply click through this link from your web page. Our crawlers will verify your link, extract the title of your web page and instantly add a link back to it. If you like you can remove the words Totally Explained and embed the link in article text.
As long as your link remains in place, we'll keep our link to you right here. Please play fair - our crawlers are watching. Your site must be closely related to this one's topic. Any kind of spamming, dubious practises or removing the link will result in your link from us being dropped and, potentially, your whole site being banned.