Search results for "Heat pipe"
showing 7 items of 7 documents
Heat in Metal Cutting
2008
This chapter provides comprehensive knowledge regarding thermal effects during the cutting process with both uncoated and coated cutting tools. Main heat sources and flowing heat fluxes into the tool, chip and workpiece are characterized and quantified. The heat distribution models that allow the analytical prediction of heat partition between the tool and the chip are specified. They consider such thermal properties as specific heat, thermal conductivity and diffusivity, Peclet thermal number, and heat transmission ratio, all as functions of temperature. Finite element method and finite difference method simulations applied to the prediction of temperature fields are outlined for turning a…
Heat pipe controlled syntheses of ionic liquids in microstructured reactors
2009
Abstract The combination of a heat pipe and a microstructured reactor allows to perform highly exothermal reactions under safe conditions. First experiments for the synthesis of 1,3-dimethylimidazolium-triflate from 1-methylimidazol and methyl triflate showed that at high flow rates of more than 5 ml/min through a single 300 μm × 500 μm wide and 400 mm long channel quantitative conversion could be achieved. This chemical reaction, known for extreme heat release, can be retained under thermal control even at much higher flow rates.
Flow chemistry: Imidazole-based ionic liquid syntheses in micro-scale
2010
The quarternization of an N-atom in the 1-methyl-imidazole with different alkylating agents was investigated to form so-called Ionic Liquids. (3-Chloropropyl)-trimethoxysilane, 1-chlorobutane, diethyl sulfate and methyl trifluoromethanesulfonate were used as alkylating agents. Reaction kinetics range from very slow to instantaneous and the reaction heat from endothermal to extremely exothermal respectively. The reactions were performed under flow conditions using different types of microstructured reactors as well as pre-structurized reactants in the micro-scale. Unusual heat management with integrated heat pipes allow safer performing of highly exothermal reactions with comparably high thr…
Heat Pipe-Cooled Microstructured Reactor Concept for Highly Exothermal Ionic Liquid Syntheses
2010
Heat pipes used for cooling of microstructured reactors are a new approach for sustainable processing also in the lab-scale within a temperature range from ambient to more than 180 °C. The main advantage of heat pipe cooling is the dynamic behavior, i.e., the cooling rate depends on the heat released. Heat pipes can also suppress thermal runaways due to their extremely short response times on momentary temperature rises. As an example, the highly exothermal synthesis of 1-ethyl-3-methylimidazolium trifluoromethanesulfonate from the respective reactants 1-ethyl-imidazole and methyltrifluoromethanesulfonate was investigated. By transferring the protocol to continuous-flow conditions in the mi…
Heat Pipe-Mediated Control of Fast and Highly Exothermal Reactions
2011
The synthesis of 1-ethyl-3-methylimidazolium ethyl-sulfate ([EMIM]EtSO4) from 1-methyl-imidazole and diethyl sulfate suffers from highly exothermal behavior. Once the activation energy barrier is reached (EA = 89 kJ mol–1), the bimolecular reaction accelerates with a high reaction enthalpy (ΔH = −130 kJ mol–1).(1-3) The excess of heat has to be concurrently dissipated to avoid hot spots or thermal runaways. Depending on the volume flow velocity of the reactants and the applied reactor temperature, the reaction zone can be shifted inside the reactor from the inlet to the outlet and vice versa. Therefore, a sophisticated thermal control, oscillating between providing activation energy and int…
The inclination effect on the performance of water-filled heat pipes
1991
Abstract Heat pipes have been used in wide ranges of applications today including solar engineering. During this research study, the inclination dependent performance of water filled heat pipes was investigated both theoretically and experimentally for solar energy applications. The results showed that the performance of water-filled heat pipes are strongly dependent on the inclination and the heat source temperatures. As a general result, the heat transfer capability of water filled heat pipes is reduced dramatically below a 45° tilt angle.
Experimental characterization of a novel configuration of thermoelectric refrigerator with integrated finned heat pipes
2021
Abstract Thermoelectric refrigerating systems (TER) are environment-friendly technologies. They have several advantages such as low maintenance costs, are less cumbersome and long lifetime. However, these systems have low coefficient of performance and are limited in achieving low temperature levels. This study investigates a new configuration of TE refrigerator employing a novel arrangement of heat sinks with integrated flat and finned heat pipes. A mathematical model is firstly developed to predict transient temperatures and cooling limit time. An experimental characterization is then performed and it includes optimization of energy consumption, cooling time, temperature levels and TE ref…