An Indirect Method for Determining the Local Heat Transfer Coefficient of Gas Flows in Pipelines

Abstract

An indirect method and procedure for determining the local heat transfer coefficient in experimental studies on the intensity of heat transfer at a gas–surface interface is described. The article provides an overview of modern approaches and technical devices for determining the heat flux or friction stresses on surfaces in the study of thermophysical processes. The proposed method uses a constant-temperature hot-wire anemometer and a sensor with a thread sensitive element fixed on the surface of a fluoroplastic substrate. A substrate with the sensor’s sensitive element was mounted flush with the wall of the investigated pipeline. This method is based on the Kutateladze–Leontiev approach (the laws of friction and heat transfer) and the hydrodynamic analogy of heat transfer (the Reynolds analogy): this is an assumption about the unity of momentum and heat transfer in a turbulent flow, which establishes a quantitative relationship between friction stresses on the heat exchange surface and heat transfer through this surface. The article presents a method for determining the speed of the developed measuring system. An example of a successful application of the proposed method in relation to the study of thermomechanical processes in the gas exchange systems of reciprocating internal combustion engines is described.

A Thermal Anemometry Method for Studying the Unsteady Gas Dynamics of Pipe Flows: Development, Modernisation, and Application

“…To evaluate the performance of the measuring system based on the developed hot-wire anemometer and sensor, dynamic calibration was carried out. It is described in detail in [ 38 ]. The principal task of dynamic calibration was to determine the time constant of all components and the measuring system as a whole.…”

“…From Figure 8 , it can be seen that the time constant τ o of the measuring system ranged from 1.3 to 3.3 ms. In this case, τ o decreased with an increased airflow speed [ 38 ]. This pattern was confirmed using classical data from other authors [ 1 , 36 ].…”

“… Dependence of the time constant τ o of a measuring system based on a hot-wire anemometer and a filament sensor on the airflow speed w [ 38 ]. …”

Development of a mathematical model for the study of transients in general primary frequency control in power systems

“…Extensive research has been conducted on the primary frequency control process, as reported in [5][6][7]. The authors investigated emergency situations with significant oscillations during frequency control in recent years.…”

Unsteady Heat Transfer of Pulsating Gas Flows in a Gas-Dynamic System When Filling and Emptying a Cylinder (as Applied to Reciprocating Machines)

“…Direct determination of α x from the removed heat flux leads to disproportionately large values of the heat-transfer coefficient since a heated local microelement creates around itself a different gas-dynamic and thermal environment than an extended hot wall. Therefore, the indirect calibration method was chosen based on the indicators of the local rate of heat transfer of a well-studied process, steady heat transfer in a long straight pipe with a circular cross-section (l/d ≈ 50) [37]. The method for determining the local heat-transfer coefficient is described in more detail in articles [37,38].…”