On the basis of completed studies, including computer modeling of the morphology of the temperature field of heat pipes and thermal measurements in the framework of the experiment, a method was developed for diagnosing the quality of heat pipes with a symmetrical structure.
Two-phase closed thermosyphons are efficient passive devices with potential for using in many heat transfer applications. One of the boiling regimes that may occur is the geyser boiling. It is a repetitive irregular process of pushing liquid without its previous evaporation in the direction of condenser. Although it does not affect time-averaged thermal performance of the device, it causes additional mechanical load and shortens the life-time of the device. Unfortunately, geysering is not well investigated, thus no precise definition exists. This paper focuses on the process of data reduction that leads to geyser boiling detection. It may be applied for various working fluids and operating conditions. Two parameters are crucial for recognizing geyser events from the background noise (pressure variations followed by the geyser): the minimum amplitude of pressure increase and waiting period between ensuing events. We compared two working fluids: water and graphene oxide nanofluid. In general, with increase of heat flux the frequency of geysers increases and their amplitude decreases.
The paper deal with heat pipe technology which is often used in electronic cooling from small voltage microchips to the high voltage electric elements. In case of cooling the high voltage electric elements have to be evaporator part and condenser part of heat pipe a separated by electrical nonconductive material, because the heat pipes are most often made of metallic materials, and thus, are electrically conductive. As a working fluids in this applications are used dielectric fluids such as fluorinert liquids. But there is still risk of the dielectric breakdown between evaporator and condenser of heat pipe. The task of the experiment is to find how the ambient temperature effect on dielectric breakdown of vapour phase of working fluid in heat pipe. In experiment was investigated dielectric breakdown between copper pipes inserted in to glass heat pipe in distance of 70 and 65 mm and temperature range -10 to -40°C. This distance simulate electric insulator distance of heat pipe used for real application of high voltage electric element cooling. For this experiment was used glass heat pipe with working fluid Fluorinert FC 72. The choice of this fluid is mainly due its excellent dielectric properties and unique combination of the thermodynamic and others properties, which makes the Fluorinert FC – 72 ideal fluid for electronic cooling used in many electronic applications.
Construction of condenser plays important role for efficient operation of energy systems. In this system a heat pipe is utilized for heat transfer. The condensation part of the heat pipe is situated on top of the heating zone. The condenser is placed in the heating zone and is used for efficient heat transfer from one medium to another. The thermal oil is used as cooling medium in the condenser. This paper analyzes the effect of different operation condition of thermal oil to thermal performance. From the collected results it is obvious that the larger mass flow and higher temperature cause better thermal performance and lower pressure drop.
The paper presents a cutting tool complex cooling system (CCS) based on the use of the first-order phase transitions for cutting process thermal stabilization by prolongation of the fusible material melting (e.g., Rose’s metal) with the help of the heat pipes.Combined cutting tools and mills with indexable inserts are designed and manufactured. The time of temperature stabilization, depending on the amount of consumable substance is calculated. It is shown that the size of the container with fusible substance can provide a melting time equal to or multiple of the execution time of technological operations.