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Heat flow rate

The heat flow is the measure of the energy transfer, which is caused by a temperature difference and leads to the temperature balance between substances. In this context, the energy is called heat.

The amount of heat that passes from one substance to another per unit of time, is the heat flow with the unit of measure Joule per second [J/s]. This is the unit of measure Watts [W] that is commonly used to indicate power.

The processes in which heat is transferred take place as heat conduction (conduction), heat flow (convection) or heat radiation (radiation).

  • Heat conduction is the transport within solid bodies or between bodies that touch each other.
  • Heat flow occurs when liquid or gaseous media move through pipes, for example, taking their heat with them.
  • The heat radiation consists of electromagnetic waves in the infrared range.
  • The process of transferring heat from one fluid through one wall to another fluid is called heat transfer

Each process is described by its own formula, with which the heat flow can be calculated.

In engineering the heat flow rate is needed for the calculation of heat losses, for the design of heat exchangers and for the determination of the energy requirements for cooling and heating. The formulas used contain purely empirically determined substance sizes, which only approximately reproduce the actual property of the medium.

The fabric sizes are also temperature-dependent and change during the processes under consideration. That is why measuring instruments with heat flow sensors are used for accurate results. The heat flow sensors exploit thermoelectric effects. During the measurement, electrical variables are detected that change as defined by the heat flow and thus allow conclusions about the heat flow.

Applications with heat flow rate

Application: Steel (Low-Alloyed Steel)

Linseis application - Steel (Low-Alloyed Steel)

Introduction and Application: Steel is a metal alloy. The most constituent parts are Iron with carbon being the primary alloying material. Carbon is the most cost-effective alloying material for iron. It exist further alloying elements such as manganese, chromium, vanadium and tungsten. Varying the amount of alloying elements remarkable change of the properties (hardness, ductility, tensile strength, phase change behavior) received. Differential Scanning Calorimetry (DSC) is a helpful instrument in order that steel get the favored properties.

Analysis using DSC: In the picture can be seen the measured specific heat flow rate of a low-alloyed steel. At 734°C happens the change in the crystal structure (from body center to face center) and change in the magnetic properties (ferromagnetic to paramagnetic) occurred. The melting point was measured at 1411°C. The liquidus temperature was measured at 1473°C.

Application: Polyethylen terephthalate (PET)

determination of glass point - PET

Introduction and Application: Polyethylene terephthalat is a thermoplastic polymer resin of the polyester family and is used in synthetic fibers, beverage, food and other liquid containers, thermoforming applications, and engineering resins often in combination with glass fiber. PET max exist both as an amorphous (transparent) and as a semi-crystalline material.

Analysis using DSC: PET shows at about 77°C a very significant endothermal glass point, when looking at partial crystalline thermo plastic materials. The relation between the exothermal cold crystallization (131°C) and the endothermal melting peak is a method for the degree of crystallization of the material. In the case of PET the crystalline part is very small, giving the material a very good transparency. This is why drinking bottles (Cola) are very often produced from PET.

Instrument to determining the heat flow

DTA PT 1600

DTA-PT1600
  • High temperature DTA
  • Modular instrument design (sample robot, gas dosing systems, muliple furnaces on a turntable, etc.)
  • Qualitative analysis of endothermic and exothermic reactions
Details

Chip-DSC 10

Linseis Chip DSC 10
  • The perfect DSC for Quality control and Education
  • Cost effective, space saving and highly innivative Chip DSC
Details

Chip-DSC 100

Linseis Chip-DSC 100
  • Unique Chip Technology – The next step in DSC
  • Modular expandable design (Sample Robot, Cooling options etc.)
Details

DSC PT 1600

Linseis Chip-DSC 100
  • Modular high temperature DSC
  • Determination of specific heat (Cp) and enthalpy from high temperature metals and ceramics
Details

STA PT 1000

STA PT 1000
  • (TGA) Thermogravimety and (DSC) Differential Scanning Calorimetry
  • True top loading TG-DSC heat flux sensors
  • Numerous user excheangable TG, TG-DSC and TG-DTA sensors for any kind of application
Details

STA PT 1600

STA oder TGA PT 1600
  • (TGA) Thermogravimety and (DSC) Differential Scanning Calorimetry
  • True top loading TG-DSC heat flux sensors
  • Numerous user excheangable TG, TG-DSC and TG-DTA sensors for any kind of application
Details

STA MSB PT 1

Linseis STA/TGA MSB
  • Magnetic Levitation Balance (MSB)
  • Separation of balance and reactor for most demanding applications
  • From Vacuum to 150 bar
  • For corrosive and toxic gases
Details

STA HP High Pressure

Linseis STA Hochdruck
  • Worlds only pressure TG-DSC (STA)
  • Combined (TGA) Thermogravimetry – (DSC) Differential Scanning Calorimetry
  • Different Gas and Vapor Dosing accessories
  • RT up to 1000/1400/ 1600/ 1800°C
  • From Vacuum up to 150 bar
Details

TIM-Tester

Linseis TIM Tester

The LINSEIS TIM-Tester (Thermal Interface Material Tester) measures the thermal impedance of sample materials and identifies an apparent thermal conductivity for a wide range of materials

  • Automatic pressure adjustment using electric actor (up to 8 MPa)
  • Automatic thickness determination using high resolution LVDT

Details