Heat sensors are basically a transducer in which an electrical signal is generated that is directly related to the overall heat rate at the surface of the heat sensor. This heat rate is then used to calculate the overall heat flux. Heat flux is known as the rate in which heat energy can transfer through a surface per unit time. These heat sensors are a great addition to a number of applications because they can be used to study the impact of fire and flames on a surface, estimate fouling on the surface of a boiler and many other ways which benefit both the safety of individuals and the overall efficiency of a process.
Perhaps the three most common applications in which to find heat sensors happen to be in the meteorology and agricultural fields, building physics, and in medical studies. Heat sensors are used in the agricultural field in order to determine the amount of energy that can be stored within soil over a certain period of time. This is done by burying multiple sensors in the soil where they are left to measure the overall heat flux of the area. Now this process is not 100% accurate as there are a lot of different factors in play that might interrupt the results, but heat sensors are the best way to measure the heat flux of an area.
They are also used in the construction of buildings, in that they are utilized to measure the heat flux inside walls in order to determine if the walls are adequately insulated or if they are allowing too much heat to pass through them. Heat sensors are also found in the medical studies field where they are used to properly measure the exchange of heat within a human body. This information is also used to design sleeping bags, clothing, and immersion suits.
So whatever your application may be, be sure to seek out a trusted heat sensor manufacturer in order to receive a heat sensor that is right for your application.