Low Temperature Coolant Research Articles

Assessment of the possibility of transferring Ukrainian district heating systems to low-temperature coolants

The analytic research was conducted for a residential building built according to a typical project in Lviv. As the research data showed, the requirements of the existing normative documents of Ukraine do not allow to significantly reduce the heat load on the heat source. Thus, the value of the maximum heat flow to the heating system decreased by 36%, and the maximum heat flow to the hot water supply system - by 7.7%, and the total maximum hourly heat consumption, respectively, decreased by 23%. In addition, studies have established that for such values of the thermal power of the heat source, a decrease in the temperature parameters of the heat carrier can lead to an increase in the consumption of the heat carrier to provide thermal energy to the house by almost 3 times. And this, in turn, for the same diameter of the pipeline, leads to an increase in specific pressure losses by more than 5 times, and, accordingly, to an increase in the power of circulation pumps, the consumption of electrical energy and the cost of these pumps. This means that at present, the transition of large systems of district heating system of Ukraine to low-temperature coolants is possible only during the reconstruction of heat networks.

Methods for Predicting the Minimum Temperature of the Outage Loop and the Maximum Power Caused by the Low-Temperature Coolant

When the feedwater valve at the outage loop of the floating nuclear power plant leaks, thermal stratification occurs in the steam generator. It causes lower water temperature in the outage loop. The extent of hazard of this phenomenon cannot be directly determined by the existing measurement parameters, which poses a threat to the operational safety of the reactor. Therefore, this study adopts two routes: data-driven combined with safety analysis system (DSAS) and mechanism model-driven combined with safety analysis system (MSAS), to propose the prediction methods for the minimum temperature of the outage loop and the maximum power caused by the low-temperature coolant. Then, the actual data are used to verify these methods and the prediction results under different initial conditions are analyzed. The results show that both the DSAS method and the MSAS method can predict the minimum temperature of the steam generator in the outage loop and the maximum power when the outage loop is put into operation, but the DSAS method has better performance under certain conditions. These methods can provide guidance to the operators to avoid reactivity insertion accident.

A dual-mode system for water purification and cooling using a thermal desalination technique coupled to a heat pump unit

Humidification-dehumidification is one of the most suitable small-scale desalination methods based on air humidification and condensation. The major energy-consuming components for a humidification-dehumidification process are a heat source for the humidifier and a cooling source for the dehumidifier. To improve the performance of these processes, the fluids were preheated using different energy sources or waste heat. In recent years, preheating air or saline water using heat from a heat pump's condenser has been explored to improve the system's performance and to produce cooling and desalination simultaneously. However, separate heat exchangers and additional solar collectors/heaters were used to preheat the second fluid. In this work, the air-cooled condenser of a heat pump has been replaced by an evaporative condenser and used as a humidifier. This configuration has been scarcely explored in the literature and requires a single heat exchanger to preheat the fluids. On the other hand, the heat pump's evaporator was used to produce low-temperature coolant, circulated through a cooling coil where the humid air from the evaporative condenser is cooled and dehumidified to produce fresh water and cooling simultaneously. This modification ensures reduced space requirement and better system performance than other heat pumps coupled to humidification-dehumidification systems for simultaneous cooling and desalination. Also, the present system operates flexibly to switch between desalination and cooling mode (mode-1) to cooling mode (mode-2). Towards this, a mathematical model of the system has been developed and analyzed under various operating conditions. The system's performance, which includes desalination yield, cooling output, gained output ratio, and coefficient of performance under each mode of operation, is studied for different ambient conditions and evaporator temperatures. The maximum desalination yield, cooling output, gained output ratio, and coefficient of performance of mode-1 are 4.55 LPH, 0.82 kWth, 3.79, and 0.75, respectively. The maximum cooling output and COP of mode-2 are 3.79 kWth and 3.82, respectively. The exergy efficiencies for mode-1 and mode-2 are 32.7 % and 29.7 %, respectively.

Finite Element Modeling of Electrochemical Polishing of Niobium in Hydrofluoric-Sulfuric Acid Electrolyte

Niobium (Nb) used in superconducting radio-frequency cavities requires smooth surface to achieve optimal performance. In this work, a finite element model that coupled electrochemistry, heat transfer, and fluid dynamics was developed to investigate the electrochemical polishing mechanisms of Nb, using experimentally measured polarization results of coupon samples as validations. The current and potential distribution, oxide growth kinetics of Nb in a complex cavity geometry was investigated as a function of temperature and coolant flow. A low temperature coolant with intermediate flow rate was found to reduce surface current and ensure oxide uniformity. These results could shed light on the design of future particle accelerators.

A Low Temperature Coolant Conditioning Cart for Testing DEF Thawing Systems

<div class="section abstract"><div class="htmlview paragraph">Diesel Exhaust Fluid (DEF) systems are required to function in cold ambient temperatures below the freezing point of DEF. Manufacturers may demonstrate compliance by following an EPA guidance procedure described below [<span class="xref">2</span>], using whole vehicles at winter test sites at −18 deg C or lower. However, commercial trucks may have multiple variants with different DEF system layouts, so it is impractical to test every possible configuration. A climatic chassis dynamometer (CCD) can also be used for this test, but this is still expensive and time consuming, and does not address the problem of complexity. Instead, much time and expense can be saved by using simulation methods to identify worst case configurations, and to demonstrate with confidence that a limited number of tests will cover the whole possible range. This methodology can further be used to show that a range of vehicles can be represented with selected rig tests in a cold chamber. Such a methodology depends on the ability to generate repeatable test data in a cold room environment. Previously published work [<span class="xref">1</span>] has shown that it is difficult to achieve a repeatable test. In particular, it is challenging to provide coolant with repeatable and accurate temperature and flow profiles, between −40 deg C and +95 deg C. A coolant cart has been developed to provide a stream of conditioned coolant, starting at −40 deg C or higher, utilizing user-specified profiles of temperature and flow rate versus time. The desired profiles were designed to match test data logged from truck engines during warmup from a typical cold overnight temperature of −22 deg C. Surprisingly, no suitable test equipment was found to be commercially available, and the task of designing and building such equipment was found to be challenging. The need to function at −40 deg C restricted the choice of components. The requirement to follow user-defined profiles for both flow and temperature, within tight error bands and following sudden changes, also required unusual care in design. A dedicated coolant cart was therefore commissioned and built. This paper documents the design and operation of the cart. Major component descriptions are provided, with circuit and input/output detail, recharge time and operator interface and processing. The end result is a cart that provides for repeatable cold room testing of tank thaw performance to support a simulation-based verification method, thereby reducing the need for whole-vehicle testing by 75%.</div></div>

Energy Saving Milk Cooling Unit Using Natural Cold and Low Temperature Coolants

Improving the energy efficiency of equipment for dairy farms is one of the most important tasks in the agriculture. A promising direction for further improving the energy efficiency of existing systems is the use of environmentally friendly refrigerants with a low freezing point (low-temperature coolants) and the potential of natural cold directly. One of the technological factors for the introduction of such systems in farms is the cooling of milk without freezing an "ice water", which requires fundamentally new technical solutions. (Research purpose) The research purpose is in increasing the energy efficiency of milk cooling using natural cold and eco-salt for the developed module. (Materials and methods) The technical characteristics of the developed module were studied in order to identify the effectiveness of primary milk cooling due to the potential of outdoor air with the possibility of further implementation of this system in farms. (Results and discussion) The article presents the results of experimental studies of an energy-saving module developed in VIM for milk cooling using natural cold and low-temperature coolants. The module is a pre-cooling unit for milk, where a closed loop with a low-temperature coolant is used instead of ground water, which allows cooling milk through the potential of external air. The article presents the dependence of the efficiency of milk cooling on the configuration of equipment and the potential of natural cold. (Conclusions) The energy efficiency of the developed milk cooling system for the Central Russia allows reducing the electricity consumption for cooling of 1 ton of milk by 15-17 kilowatt-hours, which on average will reduce financial costs by 50 percent. The introduction of a developed energy-saving module to existing cooling systems in dairy farms is proposed.

STUDY OF THE INFLUENCE OF COVERINGS OF EXTENDED RADIATING PIPES ON THEM HEAT RADIATION, WHEN HEATING LARGE OBJECTS AND HEATING INDUSTRIAL ROOMS

It is shown that for heating rooms and objects large in length and volume, the use of extended emitting pipes is most appropriate. A method for heating extended objects is described, in which the principle of radiation from radiating pipes with a length of more than 30 m is used in a garage-defroster of railway cars. The heating system of the garage-defroster includes a firebox-heat generator, long pipes of 90 m along the wagons, the control and instrumentation system A. The firebox and the control and instrumentation cabinets are installed in a separate room. The defrost system circuit is essentially a large emitter. The entire heat-radiating circuit is a closed system of direct and return pipes through which a low-temperature (300–400 °C) coolant circulates. The industrial operation of such a system at one of the Ukrainian factories has confirmed the advantages in comparison with the known defrosting systems: reliability, easy operation, high efficiency, safety and environmental friendliness, low capital costs, a minimum of instrumentation and automation, minimal thermal inertia. Ways of increasing the uniformity of temperature and heat radiation from pipes are considered: recirculation of the coolant in the working circuit and applying coatings with different emissivity to the pipe surface. So, with a recirculation rate of the coolant in the working circuit of the industrial defrosting system from 3 to 5, the temperature difference between the surface of the emitting pipes at the first and distant cars was 100 or more degrees. Therefore, cars that are closer to the coolant entrance to the system defrosted faster than others. Two new methods for controlling the radiation intensity of long pipes along their length are proposed: coating coatings with different emissivity on the surface of pipes and coating with maximum and minimum emissivity, which alternate between themselves, around the perimeter of the rings. The results of laboratory experiments on the dependence of the heat radiation of pipes on the methods of applying special coatings to them are shown, which showed that coating in a certain order allows you to change the nature of the distribution of temperatures and heat radiation on surrounding surfaces, significantly reducing their decrease along the length of the radiating pipe. Ref. 18, Fig. 4.

On the development of an optimized multiprobe cryo-ablation plan using immerse boundary method and genetic algorithm

Cryosurgery is becoming an effective method to treat undesired tumor tissue via the application of extremely low temperature coolant flowing through a probe. To maximize cryoinjury in the targeted tumor region, multiple cryoprobes are simultaneously employed to freeze the surrounding tumor tissues. In order to minimize cryosurgical injury to the surrounding health tissues, the cryoprobe localization for each specific tumor is critical. We developed finite difference analysis to calculate the freezing process during cryosurgery. According to our experimental data, the simulation results from the Pennes equation coupled with immersion boundary method (IBM) are consistent with the experimental data, with a maximum error of ±8.12%.We further incorporate a genetic algorithm as a planning tool to address the problem in connection to be interactive positioning of the cryoprobes and the freezing process duration during the pre-operative stage. Several optimization scenarios are judiciously investigated to emphasize different performance variables. Key results have revealed that this computerized approach is highly efficient one for selecting optimized multiple operational parameters.

Effectiveness of using low-temperature coolants in machining to enhance durability of AISI 316L stainless steel for reusable biomedical devices

Austenitic stainless steels are currently used for the manufacture of reusable medical instruments, thanks to their combination of elevated strength, corrosion resistance, biocompatibility and low cost. However, during their service life, they are subjected to repeated sterilization cycles, which lead to the loosening of the surface oxide stability and, thus, decrease their durability.In the present study, the influence of different machining cooling conditions on the in-service corrosion behaviour of the AISI 316L stainless steel is investigated with the aim of increasing its resistance to the sterilization cycles. In particular, the effects of low-temperature coolants, namely Liquid Nitrogen (LN2) and gaseous Nitrogen (N2) cooled by LN2 to -100 °C, were investigated and compared to those of dry and wet cutting.The machined surface integrity was characterized in terms of microstructure, hardness, residual stresses and surface roughness. Electrochemical studies, making use of potentiodynamic and cyclic polarization tests, were carried out to evaluate the corrosion resistance of the machined surfaces.It was found that the AISI 316L microstructure near the machined surface was significantly affected by the machining cooling strategies The effectiveness of using low-temperature coolants in machining of stainless steels for the manufacture of reusable medical devices was therefore demonstrated.

Enhancement of corrosion resistance to sterilization stages of a biomedical grade AISI 316L stainless steel by means of low-temperature machining

Austenitic stainless steels are currently used for the manufacture of reusable medical instruments, thanks to their combination of elevated strength, corrosion resistance, biocompatibility and low cost. However, during their service life, they are subjected to repeated sterilization cycles, which lead to the loosening of the surface oxide stability and, as a consequence, the decrease of their durability.In the present study, the in-service corrosion behaviour of the AISI 316L stainless steel was investigated after being machined using two low-temperature coolants, namely Liquid Nitrogen (LN2) and gaseous Nitrogen (N2) cooled by LN2 to -100°C, as well as using a conventional cutting fluid.Results showed that the AISI 316L microstructure near the machined surface was significantly affected by the machining cooling strategies with the generation of a hardened and more compressed layer when low-temperature coolants were used. Such surface integrity enhancements contributed to improve both the general and localized corrosion resistance to sterilization stages. From this basis, machining using low temperature coolants can be considered a suitable technique to manufacture medical devices of increased durability.

Effect of Cryogenic Machining for Titanium Alloy Based on Indirect, Internal and External Spray System

Due to the excellent properties of Ti-6Al-4V titanium alloy such as lightweight, high wear and corrosion resistance and able to maintain high strength at high elevated temperature, this material has been used mostly in aerospace and biomedical industries. However, titanium alloy being considered as a hard-to-cut material with poor machinability due to its low thermal conductivity which leads to the excessive tool wear during machining and requires high machining cost. To overcome these problems, cryogenic machining has been taken place as a promising method for machinability improvement in terms of tool wear reduction, lower energy consumption and low machining cost. Even though this method has been implemented for titanium alloy machining, it is difficult to handle the excessive extremely low-temperature coolant (up to -150 ℃) that exposed directly to the workpiece. As a result, the workpiece hardness will be increased, hence will increase the required cutting force for the machining process. In concern with the problem, this paper presents a novel cryogenic cooling mechanism (indirect cryogenic cooling) that will be used as one of the cooling and lubrication strategy. The performance of the indirect cryogenic cooling will be compared with flood cooling, Minimum Quantity Lubrication (MQL) and conventional cryogenic cooling method by using the external and internal spray system. Liquid nitrogen (LN2) being selected as the cooling medium in this work since its temperature can reach lower -196 ℃, odorless and more environmentally friendly. A specially designed tooling kit that able to supply the liquid nitrogen to the cutting tool internally is used in this method. The developed indirect cryogenic supply method able to improve the machinability of Ti-6Al-4V. The cutting force is reduced by 54% and the tool life is improved by 90% compared to the conventional flood coolant strategy.

A magnetic levitation rotating plate model based on high-Tc superconducting technology

With the wide requirements of the training aids and display models of science, technology and even industrial products for the public like schools, museums and pleasure grounds, a simple-structure and long-term stable-levitation technology is needed for these exhibitions. Opportunely, high temperature superconducting (HTS) technology using bulk superconductors indeed has prominent advantages on magnetic levitation and suspension for its self-stable characteristic in an applied magnetic field without any external power or control. This paper explores the feasibility of designing a rotatable magnetic levitation (maglev) plate model with HTS bulks placed beneath a permanent magnet (PM) plate. The model is featured with HTS bulks together with their essential cryogenic equipment above and PMs below, therefore it eliminates the unclear visual effects by spray due to the low temperature coolant such as liquid nitrogen (LN2) and additional levitation weight of the cryogenic equipment. Besides that, a matched LN2 automation filling system is adopted to help achieving a long-term working state of the rotatable maglev plate. The key low-temperature working condition for HTS bulks is maintained by repeatedly opening a solenoid valve and automatically filling LN2 under the monitoring of a temperature sensor inside the cryostat. With the support of the cryogenic devices, the HTS maglev system can meet all requirements of the levitating display model for exhibitions, and may enlighten the research work on HTS maglev applications.

Mechanical and tribological properties of ice-bonded abrasive polishing tools

This article covers the efforts on characterising ice-bonded abrasive polishing tool in terms of the mechanical and tribological properties such as hardness, coefficient of friction, and wear rate. These studies were attempted on the tools prepared at different temperatures ranging from −10 °C to 0 °C with a view to identify the condition suitable to prepare ice-bonded abrasive polishing tool for effective polishing of Ti–6Al–4V alloy specimen. It also presents the methods adopted to determine various properties of ice-bonded abrasive polishing tool. Hardness was estimated from the measured penetration depth of cone shape indenter into the tool, coefficient of friction was determined from the change in power drawn by the motor rotating the tool mould, and wear behaviour of tool was assessed from the melting rate of the tool determined from the change in height of ice-bonded abrasive polishing tool at different stages of polishing. From the results of this study, it is clear that ice-bonded abrasive polishing tool prepared at −4 °C has possessed sufficient hardness, coefficient of friction, and reasonable wear rate suitable for polishing of Ti–6Al–4V specimens. This article also covers the details of low-temperature coolant supply unit developed to prepare the ice-bonded abrasive polishing tool at any desired temperature between 0 °C and −40 °C and thus to maintain it for a long time. Polishing studies with such ice-bonded abrasive polishing tool showed 72% improvement in finish after 90 min of polishing of Ti–6Al–4V specimen with tool, prepared at −4 °C.

Effects of Electromagnetic Heating on Quick Freezing

Purpose: Quick freezing is widely used in commercial food storage. Well-known freezing techniques such as individual quick freezing require a low-temperature coolant and small cuts for the heat-transfer efficiency. However, the freezing method for bulk food resembles techniques used in the 1970s. In this study, electromagnetic (EM) heating was applied to improve the quick freezing of bulk food. Methods: During freezing, the surface of food can be rapidly cooled by an outside coolant, but the inner parts of the food cool slowly owing to the latent heat from the phase change. EM waves can directly heat the inner parts of food to prevent it from freezing until the outer parts finish their phase change and are cooled rapidly. The center temperature of garlic cloves was probed with optical thermo sensors while liquid nitrogen (LN) was sprayed. Results: When EM heating was applied, the center cooling time of the garlic cloves from freezing until -10°C was 48 s, which was approximately half the value of 85 s obtained without EM heating. For the white radish cubes, the center cooling time was also improved, from 288 to 132 s. The samples frozen by LN spray with EM heating had a closer hardness to the unfrozen samples than the samples frozen by LN only. Conclusions: The EM heating during quick freezing functions to maintain the hardness of fresh food by reducing the freezing time from 0 to -10°C.

System Design and Performance Analysis of a Quick Freezer using Supercooling

Purpose: This study was conducted for enhancing the performance of a conventional quick freezer by introducing the supercooling state, using a low-temperature coolant. Methods: In the present investigation, the supercooling process was executed prior to quick freezing for reducing the time by which the temperature passes the zone of maximum ice crystal formation. Every food has different nucleation points and hence, we used silicone oil as the coolant for supercooling for easy modification of temperature. Additionally, for quick freezing, we used liquid nitrogen spray. Results: Using the heat exchangertype precooler with silicone oil, the temperature of the chamber was easily changed for enabling supercooling. Particularly, the results of the freezing test with garlic indicated that this system improved the hardness of garlic after it was thawed, compared to the conventional freezing method. Conclusions: Before quick freezing, if the food item is subjected to the supercooling state, the time from nucleation to the temperature reaching the frozen state (-5°C, which is the maximum ice crystal formation zone) will be shorter than that incurred using quick freezing alone. The combination of the heat exchangertype supercooler and liquid nitrogen sprayer is expected to serve as a promising technology for improving the physicochemical qualities of frozen foods.

New fields of application of regenerative cooling-gas machines

This paper describes the application of a low-temperature cooling. The most relevant schemes of low-temperature coolant for needs of cryochemical technologies using refrigeration gas Stirling machine were shown.

Liquid metal as energy transportation medium or coolant under harsh environment with temperature below zero centigrade

The current highly integrated electronics and energy systems are raising a growing demand for more sophisticated thermal management in harsh environments such as in space or some other cryogenic environment. Recently, it was found that room temperature liquid metals (RTLM) such as gallium or its alloys could significantly reduce the electronics temperature compared with the conventional coolant, like water, oil or more organic fluid. However, most of the works were focused on RTLM which may subject to freeze under low temperature. So far, a systematic interpretation on the preparation and thermal properties of liquid metals under low temperature (here defined as lower than 0°C) has not yet been available and related applications in cryogenic field have been scarce. In this paper, to promote the research along this important direction and to overcome the deficiency of RTLM, a comprehensive evaluation was proposed on the concept of liquid metal with a low melting point below zero centigrade, such as mercury, alkali metal and more additional alloy candidates. With many unique virtues, such liquid metal coolants are expected to open a new technical frontier for heat transfer enhancement, especially in low temperature engineering. Some innovative ways for making low melting temperature liquid metal were outlined to provide a clear theoretical guideline and perform further experiments to discover new materials. Further, a few promising applied situations where low melting temperature liquid metals could play irreplaceable roles were detailed. Finally, some main factors for optimization of low temperature coolant were summarized. Overall, with their evident merits to meet various critical requirements in modern advanced energy and power industries, liquid metals with a low melting temperature below zero centigrade are expected to be the next-generation high-performance heat transfer medium in thermal managements, especially in harsh environment in space.

Effect of Return Bend and Entrance on Heat Transfer in Thermally Developing Laminar Flow in Round Pipes of Some Heat Transfer Fluids With High Prandtl Numbers

Abstract The paper presents experimental results and analysis of heat transfer in a thermally developing region of round pipes for three fluids typically used as low temperature coolants, in the range of 0–−40°C. The experiments were performed at low Re (200–1000) and high Pr (80–140) numbers that are typically found in secondary refrigeration loop conditions. The effect of horizontal U-bend is also presented. It is shown that the positive effect of thermal development (high Nu number) lasts long because of the technically significant length of the thermally developing region. Secondary flows developed in and after the U-bend are so significant that they have almost an identical effect as the thermal development at the pipe entrance. That is a reason for the extremely good performance of the heat exchangers with secondary refrigerants in laminar flow regimes. Experimental data are presented with developed empirical correlations, which show good relationships to several existing correlations.

Modular front-end cooling module architecture for future powertrains

Cooling system development is driven by upcoming CO2 reduction legislation. Valeo highlights an innovative cooling system architecture, which uses two modular main coolant radiators in the vehicle frontend. This newly developed “Ultimate Cooling” system has both low temperature and high temperature coolant loops, which are connected with each other. It allows together with an adapted control strategy to optimize the available heat dissipation capacity installed by the radiators in the vehicle front end. Results of measurements and simulation show the advantages of this new system in a demo-car with a Euro-4 diesel engine (50 kW/l) and a highly charged (80 kW/l) Euro-6 diesel engine.

Thermal-mechanical analyses of the ITER shielding blanket designs

Abstract Thermal-mechanical analyses were performed for the ITER shielding blanket design to define the performance of the structures when subjected to thermal loads, the internal pressure and the electromagnetic forces. The shielding blanket design under consideration has austenitic steel structure, low temperature and pressure water coolant, and a copper layer coated with beryllium for the first wall. The first wall is structurally integrated with the shielding blanket by thin lateral walls welded to the back plate. At the side wall of the sector, the internal pressure is sustained by the adjacent canisters. Two-dimensional analyses of the equatorial cross-section were carried out using generalized plane strain boundary conditions to simulate the out of plane structure behavior. The mechanical loads used in the analyses consist of an internal coolant pressure of 2 MPa and electromagnetic loads on the first wall due to plasma disruption events of 1 MPa for outboard sections. Two thermal loads were included: a surface heat flux of 50 W cm −2 on the first wall and nuclear heating from the neutronics analyses.