Heat Transfer Index (HTI) Tests

Heat transfer is the movement of heat from one substance or material to another. Heat transfer occurs through three main systems: conduction, radiation and convection. The main ways of heat transfer in a fired heater are radiation and convection. Heat transfer rate refers to the amount of heat transferred per unit time. Heat transfer rate is measured in joules per second.

Heat transfer can be detected by measuring the resulting temperature change. The temperature of an object is proportional to the average kinetic energy of its atoms or molecules. As the temperature of a substance increases, the average speed of its atoms or molecules increases.

The heat transfer index (HTI) is calculated from the average time it takes to achieve a temperature rise of 24 degrees with a copper disk calorimeter. The heat transfer index is to determine the ability of clothing to delay heat transfer from the flame. This index is widely used in textiles for personal protective equipment. A heat transfer index tester is a device that measures heat conduction through materials or material assemblies exposed to heat flow from the flame of a gas burner.

In short, the movement of heat from one object to another is called heat transfer. Heat transfer is defined as the process by which molecules move from a high-temperature region to a low-temperature region. In other words, heat is the flow of energy from an object at a higher temperature to an object at a lower temperature. It is the temperature difference between two neighboring objects that causes heat transfer. Heat transfer continues until the two objects reach thermal equilibrium and are at the same temperature.

In thermodynamics, the heat transfer coefficient (film coefficient or film efficiency) is the constant of proportionality between heat flow and the thermodynamic driving force for heat flow (i.e., temperature difference).

Heat transfer has wide applications in the operation of numerous devices and systems. Heat transfer principles are used to maintain, increase or decrease temperature in a wide variety of situations.

A heat transfer index (HTI) tester is a device that measures heat conduction through materials or material assemblies exposed to heat flow from the flame of a gas burner. The heat transfer index is meant to rank the ability of clothing sets to delay heat transfer from the flame. This index is widely used in textiles for personal protective equipment.

The heat transfer index tester is used to measure heat conduction through materials or mechanisms used in protective clothing and gloves when exposed to a specific convective heat source. When performing the heat transfer index test, a horizontally mounted sample is exposed to a heat flux of 80 kW/m2 from the flame of the burner beneath it. The heat passing through the sample is measured at the top by contacting the sample with a copper disc calorimeter defined in the ISO 9151 standard. The temperature rise time of 24 degrees is recorded and the average of the three results is calculated as the Heat transfer index (HTI).

The standard “ISO 9151: Protective clothing against heat and flame - Determination of heat conduction in case of exposure to flame” developed by the International Organization for Standardization (ISO) describes a test method for determining heat conduction through materials or material assemblies used in protective clothing. Once testing is complete, materials are ranked by comparing their heat transfer indices, which provide an indication of relative heat conduction under specified test conditions. However, the heat transfer index is not considered a measure of the duration of protection provided by the tested materials under actual use conditions.

Among the numerous testing, measurement, analysis and evaluation studies it provides for businesses in various sectors, our organization also provides heat transfer index (HTI) testing services with its trained and expert staff and advanced technological equipment.