Secondary Heat Source Research Articles

A 4E Analysis of a Solar Organic Rankine Cycle Applied to a Paint Shop in the Automotive Industry

In a conventional automotive manufacturing plant, the paint shop alone can represent 36% of the total energy consumption, making it the most demanding area in terms of electricity and fossil fuel energy consumption. This study explores the possibility of decentralizing the production of electrical power and heat simultaneously, using an Organic Rankine Cycle (ORC) system integrated with a Parabolic Trough Collector (PTC) in a paint shop. To date, no similar system has been explored or implemented by the automotive industry. To increase the efficiency of the integrated system, wasted heat generated during the paint manufacturing process is recovered and used to pre-heat the organic fluid in the ORC system. A 4E analysis (Energy, Exergy, Economic, and Environmental) is conducted to determine the practical viability of the proposed system. When applied to the southern region of the USA, this system’s installed capacity is projected to be 11 times higher than the two unique SORC pieces of equipment currently running in Louisiana and Florida. The goals are to reduce the reliance on external primary energy sources and decrease the carbon emission footprint from production activity. The system is evaluated for a location in Alabama, USA. The designed SORC, using toluene, can produce 712.2 kWel net and 13,132 kg/h of hot water, with an overall energy efficiency of 31.02%; exergy efficiency of 34.23; and ORC efficiency of 27.70%. This leads to an electrical energy saving of 5.9% for the manufacturing plant. The regenerative thermal oxidizer (RTO) heat exchanger, the secondary heat source of the system, has the highest exergy destruction—3583 kW. The system avoids the emission of 4521 tCO2 per year. A payback period of 10.16 years for the proposed system is estimated. Considering a planning horizon of 10 years, the investment in the system is also justified by a benefit–cost analysis.

Methodological Solutions for Predicting Energy Efficiency of Organic Rankine Cycle Waste Heat Recovery Systems Considering Technological Constraints

Solving strategic IMO tasks for the decarbonization of maritime transport and the dynamics of its controlling indicators (EEDI, EEXI, CII) involves the comprehensive use of renewable and low-carbon fuels (LNG, biodiesel, methanol in the mid-term perspective of 2030, ammonia, and hydrogen to achieve zero emissions by 2050) and energy-saving technologies. The technology of regenerating secondary heat sources of the ship’s power plant WHR in the form of an Organic Rankine Cycle (ORC) is considered one of the most promising solutions. The attractiveness of the ORC is justified by the share of the energy potential of WHR at 45–50%, almost half of which are low-temperature WHR (80–90 °C and below). However, according to DNV GL, the widespread adoption of WHR-ORC technologies, especially on operating ships, is hindered by the statistical lack of system prototypes combined with the high cost of implementation. Developing methodological tools for justifying the energy efficiency indicators of WHR–ORC cycle implementation is relevant at all stages of design. The methodological solutions proposed in this article are focused on the initial stages of comparative evaluation of alternative structural solutions (without the need to use detailed technical data of the ship’s systems, power plant, and ORC nodes), expected indicators of energy efficiency, and cycle performance. The development is based on generalized results of variation studies of the ORC in the structure of the widely used main marine medium-speed diesel engine Wärtsilä 12V46F (14,400 kW, 500 min−1) in the operational load cycle range of 25–100% of nominal power. The algorithm of the proposed solutions is based on the established interrelationship of the components of the ORC energy balance in the P-h diagram field of thermodynamic indicators of the cycle working fluid (R134a was used). The implemented strategy does allow, in graphical form, for justifying the choice of working fluid and evaluating the energy performance and efficiency of alternative WHR sources for the main engine, taking into account the design solutions of the power turbine and the technological constraints of the ORC condensation system. The verification of the developed methodological solutions is served by the results of comprehensive variation studies of the ORC performed by the authors using the professionally oriented thermoengineering tool “Thermoflow” and the specification data of Wärtsilä 12V46F with an achieved increase in energy efficiency indicators by 21.4–7%.

Research on thermal characteristics modeling of CNC machine tools based on submodel method

To improve the accuracy of thermal characteristics analysis of CNC machine tools, a modeling method for the thermal characteristics of CNC machine tools based on submodel method is proposed in this paper. In this method, the thermal-structural coupling calculation of the feed system and spindle system is initially completed in ABAQUS to obtain temperature and deformation results of the submodels. Subsequently, User Define Function (UDF) in Fluent is used to extract the temperature information from the surface of the submodels. The obtained surface temperature data is then imported into the overall machine model for fluid-structure coupling heat transfer calculation. The model developed in this study takes into account factors such as the dynamic heat generation of the heat source, the cooling fan system, and the secondary heat source effect of the cutting fluid. To validate the approach, a thermal characteristics experiment was conducted, and the research results demonstrate that the thermal analysis model established in this paper exhibits both high accuracy and efficiency. During the 180 min of machine operation, the thermal displacement between the tool tip and the workpiece increased. The maximum thermal deformation of the machine tool tip was 40.83 [Formula: see text], primarily observed in the X and Y directions.

Complex Use of the Main Marine Diesel Engine High- and Low-Temperature Waste Heat in the Organic Rankine Cycle

The decarbonization problem of maritime transport and new restrictions on CO2 emissions (MARPOL Annex VI Chapter 4, COM (2021)562) have prompted the development and practical implementation of new decarbonization solutions. One of them, along with the use of renewable fuels, is the waste heat recovery of secondary heat sources from a ship’s main engine, whose energy potential reaches 45–55%. The organic Rankine cycle (ORC), which uses low-boiling organic working fluids, is considered one of the most promising and energy-efficient solutions for ship conditions. However, there remains uncertainty when choosing a rational cycle configuration, taking into account the energy consumption efficiency indicators of various low-temperature (cylinder cooling jacket and scavenging air cooling) and high-temperature (exhaust gas) secondary heat source combinations while the engine operates within the operational load range. It is also rational, especially at the initial stage, to evaluate possible constraints of ship technological systems for ORC implementation on the ship. The numerical investigation of these practical aspects of ORC applicability was conducted with widely used marine medium-speed diesel engines, such as the Wartsila 12V46F. Comprehensive waste heat recovery of all secondary heat sources in ORC provides a potential increase in the energy efficiency of the main engine by 13.5% to 21% in the engine load range of 100% to 25% of nominal power, while individual heat sources only achieve 3% to 8%. The average increase in energy efficiency over the operating cycle according to test cycles for the type approval engines ranges from 8% to 15% compared to 3% to 6.5%. From a practical implementation perspective, the most attractive potential for energy recovery is from the scavenging air cooling system, which, both separately (5% compared to 6.5% during the engine’s operating cycle) and in conjunction with other WHR sources, approaches the highest level of exhaust gas potential. The choice of a rational ORC structure for WHR composition allowed for achieving a waste heat recovery system energy efficiency coefficient of 15%. Based on the studied experimental and analytical relationships between the ORC (generated mechanical energy) energy performance (Pturb) and the technological constraints of shipboard systems (Gw), ranges for the use of secondary heat sources in diesel operational characteristic modes have been identified according to technological limits.

Highly Efficient and Selective Light-Driven Dry Reforming of Methane by a Carbon Exchange Mechanism.

Dry reforming of methane (DRM) is a promising technique for converting greenhouse gases (namely, CH4 and CO2) into syngas. However, traditional thermocatalytic processes require high temperatures and suffer from low selectivity and coke-induced instability. Here, we report high-entropy alloys loaded on SrTiO3 as highly efficient and coke-resistant catalysts for light-driven DRM without a secondary source of heating. This process involves carbon exchange between reactants (i.e., CO2 and CH4) and oxygen exchange between CO2 and the lattice oxygen of supports, during which CO and H2 are gradually produced and released. Such a mechanism deeply suppresses the undesired side reactions such as reverse water-gas shift reaction and methane deep dissociation. Impressively, the optimized CoNiRuRhPd/SrTiO3 catalyst achieves ultrahigh activity (15.6/16.0 mol gmetal-1 h-1 for H2/CO production), long-term stability (∼150 h), and remarkable selectivity (∼0.96). This work opens a new avenue for future energy-efficient industrial applications.

New working fluids for the use of heat secondary sources in mining technologies

Production cost of mining enterprises can be significantly reduced when using secondary heat. A large volume of secondary heat sources has a temperature potential of no higher than 50°C. To generate additional electricity using secondary heat it has been proposed to use installations with the Rankine thermodynamic cycle in mining enterprises. The paper aim is to study the thermodynamic efficiency of using R-1234yf and R-744 in the equipment, which uses the secondary heat of mining technologies for evaporation of these working fluids. R-1234yf is a freon that belongs to the class of hydrofluoroolefins and has a much lower level of global warming potential than other ozone-depleting substances. R-744 is carbon dioxide, which belongs to a natural, non-toxic and non-flammable working substance. It has been determined that the thermodynamic efficiencies of using R-1234yf and R-744 are 10% and 6.3%, respectively. The thermodynamic efficiency has been calculated for the temperature range from 50° to 20°C, which is typical for a large volume of secondary heat sources in mining technologies.

Thermal–mechanical model for machining with chamfered insert considering tool flank wear

The deformation of material leads to severe thermal–mechanical effects during metal cutting with chamfered insert. The high cutting temperature on the contact face results in the wear of the insert which is a critical issue. However, there is still a lack of a comprehensive understanding of thermal–mechanical effects, especially with respect to the presence of the tool flank wear. To address this, an analytical thermal–mechanical model is developed in this paper for the prediction of the temperature distribution with a worn insert based on a modified slip-line field approach. Firstly, an analytical slip-line field model is introduced based on material plasticity and plowing theory considering the tool flank wear. The structure of the slip-line field model, especially at the dead metal zone and the flank zone, is modified to reveal the material flow mechanism. Then, heat sources, including primary heat source, secondary heat source, tertiary heat source, and fourth heat source, are clarified to explain the heat generation phenomenon in the cutting process. In addition, a cutting temperature field model is developed to show the effect of tertiary heat source based on the imaginary heat source theory. Finally, the slip-line field geometry and temperature distribution are extracted from two-dimensional finite element simulation to verify the proposed model. And orthogonal experiments are carried out for measuring the maximum cutting temperature. The good agreement of predicted results, simulated results, and experimental results verifies the accuracy of the proposed model.

Temperature regulation in the Balkan spadefoot (Pelobates balcanicus Karaman, 1928) at the beginning of nocturnal activity.

On land, the amphibians interact with the environment in a complex way-even small changes in the physiological conditions may significantly impact the behaviour and vice versa. In ectothermic tetrapods, the transition from inactive to active phase may be related to important changes in their thermal status. We studied the thermal ecology of adult Balkan spadefoots (Pelobates balcanicus Karaman, 1928) in northeastern Bulgaria. These toads spend the daytime buried between 10 and 15 cm in sandy substrates, and emerge after sunset. On the substrate, their thermal energy exchange is defined by the absence of heat flow from the sun. Secondary heat sources, like stored heat and infrared radiation from the soil play an important role for the thermal balance of the active spadefoot toads. At the beginning of their daily activity, we measured substrate temperature (at a depth of 11–12 cm), toad’s surface body temperature, and also provided thermal profiles of the animals and the substrate surface in their microhabitats. In animals which recently emerged from the substrate, the temperature was comparatively higher and was closer to that of the subsoil on the spot. After that, body temperature decreased rapidly and continued to change slowly, in correlation with air temperature. We detected a temperature gradient on the dorsal surface of the toads. On the basis of our measurements and additional data, we discuss the eventual role of air humidity and the effects of surface and skin water evaporation on the water balance and activity of the investigated toads.

Laser-TIG welding of galvanized steel – numerical and experimental assessment of the effect of arc in various setups

The technology of laser-TIG welding utilizes the arc as a secondary heat source during laser welding. In TIG-leading configuration, the low-current arc precedes the beam to preheat the material. The numerical simulations representing various setups combining laser and arc were performed to study the changes of thermal cycles on the interface of thin metal sheets of overlap joint. The relations between the position of the arc towards the beam, additional heat input, and temperature gradients are discussed. The technology of laser-TIG welding of zinc-coated deep-drawing steel was experimentally applied in the same joint configuration. A good agreement between the calculated and experimental welds was achieved. The arc current less than 40 A did not cause the vaporization, neither oxidation of zinc coating on the interface surface of metal sheets. Nevertheless, the quality of laser-TIG welds was better compared to laser welds. The 40A arc current increased the heat input by about 50% and led to an almost 60% decrease in cooling rate compared to autonomous laser welding. Prolonged heating and cooling time are the key factors of improving the weld quality.

Research of Organic Rankine Cycle Energy Characteristics at Operating Modes of Marine Diesel Engine

The publication examines one of the most effective ways to decarbonize marine transport, specifically the secondary heat sources utilization in the cogeneration cycle of the main engines. The research focuses on the optimization of Organic Rankine Cycle (ORC) performance parameters by combining them with the exhaust energy potential of a medium speed four-stroke main diesel engine in ISO8178 (E3) load cycle modes. Significant advantages were not found between the evaluated Wet-, Isentropic-, and Dry-type liquids (R134a, R141b, R142b, R245fa, Isopentane) in terms of ORC energy performance with a 10% difference. The use of a variable geometry turbogenerator turbine with Dry-type (R134a) working fluid is characterized by the highest ORC energy efficiency up to 15% and an increase in power plant (including turbogenerator generated mechanical) by 6.2%. For a fixed geometry turbine, a rational control strategy of the working fluid flow (Gd.sk − πT) is determined by the priorities of the power plant in certain load modes. The influence of the overboard water temperature on the ORC energy indicators does not exceed ±1%; however, it influences the thermodynamic saturation parameters of the working fluid condensation and, in connection with that, the fluid selection.

Analytical thermal model of orthogonal cutting process for predicting the temperature of the cutting tool with temperature-dependent thermal conductivity

High temperatures generated in cutting processes significantly affect the surface integrity of machined parts and tool wear, leading to workpiece thermal damage, tensile residual stresses in the workpiece and a reduction in tool life. In recent years, different analytical thermal models to predict cutting temperatures have been developed in literature based on 2D modeling of the cutting process and the assumption that thermal conductivities of workpiece and chip are not dependent on temperature. However, this dependence of conductivity on temperature may have a significant influence on predicted temperatures and must be taken into account. In this paper, a thermal model of the orthogonal cutting process that considers thermal conductivity of materials (chip and tool) to be dependent on temperature is developed. A linear variation of thermal conductivity with temperature is assumed for chip (workpiece) and tool materials. The model is based on application of: (1) the Kirchhoff transformation in order to convert the nonlinear heat conduction problem into a linear one, (2) the theory of moving and stationary heat sources in semi-infinite and infinite mediums in order to model primary and secondary deformation zones and (3) imaginary heat sources to meet adiabatic boundary conditions in the chip and tool. Imaginary heat sources were defined in the thermal model proposed in this paper in such a way that the effect of the tool-chip interface dimensions and of cutting tool width on the tool temperature could be taken into account. This allows the temperature on the rake face and lateral faces of the tool to be predicted. To this end, a new methodology that considers the temperature-dependent thermal conductivity of materials was developed in order to estimate heat partition ratio along the secondary heat source (tool-chip interface), which is assumed to be non-uniform. Orthogonal cutting tests were also performed in order to verify model predictions by comparing them to tool temperature distributions measured using an IR camera.

Thermal modelling of cutting tool temperatures and heat partition in orthogonal machining of high-strength alloy steel

Cutting temperatures and heat partition into the cutting tool are critical factors that significantly affect tool life and part accuracy during metal removal operations, especially in dry machining. Among many thermal modelling studies, uniform heat partition ratio, and/or uniform heat intensity along the tool-chip interface are frequently assumed. This assumption is not valid in actual machining and can lead to erroneous estimated results in the presence of sticking and sliding friction zones. Therefore, it is necessary to accurately predict the cutting tool temperature and heat partition during machining. This paper presents an analytical thermal modelling approach which considers the combined effect of the primary and the secondary heat sources and determines the temperature rise and non-uniform heat partition ratio along the tool-chip interface. Cutting tests were conducted on AISI/SAE 4140 high-strength alloy steel using carbide cutting tools over a wide range of cutting speeds. Cutting temperatures were measured experimentally using an infrared thermal imaging camera. Experimentally established sticking and sliding friction regions were used to evaluate non-uniform frictional heat intensity along the tool-chip interface. The temperature matching condition along the tool-chip interface leads to the solution of distributed non-uniform heat partition ratio by solving a set of linear equations through programming in MATLAB®. Experimental results show to be consistent well with those obtained from the thermal model, yielding a relative difference of predicted average tool-chip interface temperature from −0.8% to 6.3%. It is found that average heat partition into the cutting tool ( RT) varies from 35% down to 15% for the entire range of cutting speeds. These results suggest that, to address the thermal problem in metal cutting, the research and development of tooling should also focus on reducing friction on the tool rake face in addition to the contribution of the combined effect of primary and secondary heat sources on temperature rise at the tool-chip interface.

Characterization of tool wear in similar and dissimilar joints of MS and SS using EAFSW

Abstract Friction Stir Welding (FSW) faces many issues while joining high strength material. In this study an external secondary heat source from a DC source kept at 4 V supply has been used to in between the tool and the workpiece to give an external heat source to FSW and use the method as Electrically Assisted Friction Stir Welding (EAFSW) process. This study represents analysis of mechanical properties of Mild steel (MS) and Stainless-Steel (SS) joint, made by both FSW and EAFSW. An effect of the secondary heat source of electric energy on the mechanical property of the joint and to the tool wear while joining similar and dissimilar material of MS and SS has also been studied. The study represented the effect of the addition of a secondary heat source of an electric current heating to FSW and the impact of various process parameters like tool rpm and feed on the tool wear. The results have been shown to express an expected tool life of WC tool material for joining mild steel and stainless steel. Th experimentation has proved the suitability of Tungsten Carbide as tool material for joining high strength material such as MS and SS. It has also been observed that with suitable utilization of process parameters and secondary heat sources, the heat at the nugget zone increases causing better mixing of the nugget zone. Due to a generation of higher heat at the nugget zone, less tangential and radial load occurs at the tool pin resulting less tool wear and better tool life.

Analysis of mechanical property of electrically assisted friction stir welding to enhance the efficiency of joints

The concept of Friction Stir Welding (FSW) technique was invented in year 1991 and since then many research have been done in the same field. To utilize the technique in various materials, many additional heat sources had been tested successfully and many such hybrid FSW methods came up. Electric Resistance Friction Stir Welding has been invented as one of the hybrid technology and produces less tear and wear of the tool with fewer defects of the joint produced. This study has been done to find the effect of secondary source of energy by electric assistance to FSW for improving the efficiency of the weld and to study the effect of various process parameters to improve the property of the weld joint of CS to IS 2062 Grade B. Design of Experiment has been applied to study the influence of the process parameters viz tool speed (rpm), electric current (Amps) and feed on the UTS of the weld. The joint has also been tested for checking the variation of the weld efficiency and hardness of the joint due to change in process parameters. The optimization of the process parameters has been done to obtain maximum Tensile strength, weld efficiency and hardness. The results of the optimization has been found to be indicating that due to the effect of addition of secondary heat source of electric current, the welding efficiency and hardness value has been found higher than the specimen joined without the secondary source.

Temperature prediction of ultrasonic vibration-assisted milling

Machining temperature is a key factor in ultrasonic vibration-assisted milling as it can significantly influence tool wear rate and residual thermal stresses. In current study, a physics-based analytical predictive model on machining temperature in ultrasonic vibration-assisted milling is proposed, without resorting to iterative numerical simulations. As the tool periodically loses contact with the workpiece under vibration, three types of tool-workpiece separation criteria are first examined based on the tool trajectory under ultrasonic vibration. Type I criterion examines whether the relative velocity between tool and workpiece in cutting direction is opposite to the tool rotation direction. Type II criterion examines whether the instantaneous vibration displacement in radial direction is larger than instantaneous uncut chip thickness. Type III criterion examines whether there is overlap between current and previous tool paths due to vibration. If no contact, the instantaneous temperature rise is zero. Otherwise, the temperature rise is predicted under shearing heat source in shear zone and secondary rubbing heat source along machined surface. A mirror heat source method is applied to predict temperature rise, considering oblique band heat sources moving in a semi-infinite medium. The proposed predictive temperature model in ultrasonic vibration-assisted milling is validated through comparison to experimental measurements on Al 6063 alloy. The proposed predictive model is able to match the measured temperature with high accuracy of 1.85% average error and 5.22% largest error among all cases. Sensitivity analysis is also conducted to study the influences of cutting and vibration parameters on temperature. The proposed model is valuable in terms of providing an accurate and reliable reference for the prediction of temperature in ultrasonic vibration-assisted milling.

Design and performance analysis of a novel Transcritical Regenerative Series Two stage Organic Rankine Cycle for dual source waste heat recovery

A Transcritical Regenerative Series Two stage Organic Rankine Cycle (TR-STORC) is proposed to improve the efficiency of existing Series Two stage ORC (STORC) architecture by combining supercritical heating in the high pressure (HP) stage and partial evaporation with regeneration in the low pressure (LP) stage. Exhaust gas and jacket water from a stationary IC engine is used as the primary and secondary heat source respectively. Using cyclopentane as working fluid, system exergy performance is analysed for a range of heat source temperatures and for different ratios of heat available between the heat sources. At lower HP evaporator pressures, lower values of vapour outlet temperatures lead to maximum power output. For a wide range of heat ratios and temperatures, TR-STORC delivers improved exergetic performance over STORC and pre-heated ORC. It is the recommended choice for all scenarios of dual source heat recovery. For the engine design point, TR-STORC delivers increased power output by up to16% and 23% than STORC and pre-heated ORC respectively. TR-STORC maintains exergetic superiority for all the working fluids investigated with maximum net power outputs exceeding STORC by15–34% and preheated ORC by 15–52%.

Performance investigation of two stage Organic Rankine Cycle (ORC) architectures using induction turbine layouts in dual source waste heat recovery

Abstract Improvement in performance of Organic Rankine Cycle (ORC) systems, particularly in the context of dual heat sources such as IC engines, leads to better return on investments. However, the choice of architecture to achieve the best performance is not evident from available literature. When two separate heat sources are present concurrently at different temperature levels with heat contents such as in IC engines, single stage pre-heated ORC and dual loop ORC are the two commonly deployed ORC architectures. In this study, two stage architectures: Series two stage ORC (STORC) and Parallel two stage ORC (PTORC) are analysed and their performance is compared against a single stage pre-heated ORC at sub-critical conditions in the utilization of high temperature (primary) exhaust gases (573–773 K) and low temperature (secondary) jacket water (353–393 K) representing IC engine waste heat conditions. Results show that STORC and PTORC are able to achieve the maximum net power output for an intermediate utilization of secondary heat source. The power output gains from two stage layouts improves significantly with a reduction in heat source temperature difference and for lower ratios of the heat available between the primary to secondary heat source. For a 2.9 MW natural gas IC engine operating at its design point, STORC delivers 8.5% more power output whereas PTORC delivers 0.3% less power output than pre-heated ORC. Compared to a dual–loop ORC, STORC presents a less complex and improved cycle architecture with a 13.1% increased power output and a 27.9% reduced heat exchanger requirements.

Flank tool wear prediction of laser-assisted milling

An analytical predictive model for flank tool wear in laser-assisted milling is proposed based on the principles of abrasive, adhesive, and diffusive wear. The laser effect is included by treating the laser beam as a heat source on top surface. Heat convection between top surface and the environment is factored into account. Isothermal boundary conditions are assumed for the laser-affected area. The laser preheating temperature field is averaged along the tool-workpiece interface as initial temperature. Next, the milling configuration is treated as orthogonal cutting followed by angular-dependent coordinate transformation at each instance. The effective force due to flank wear is calculated by integrating the stress component along the chip cross section and wear land, and the average stress on tool-workpiece interface due to flank wear is calculated based on the effective force and contact area. The average temperature along the interface is derived through imaginary heat source method with secondary and rubbing heat sources considered. The flank wear rate prediction considers abrasion, adhesion, and diffusion. The proposed model is validated through experimental measurements on the laser-assisted milling of K24 nickel-based superalloy, and a sensitivity analysis with respect to three cutting and two laser parameters is conducted. The proposed predictive model is able to match the wear progressions during steady state wear region in less than two minutes with high accuracy of 6.48% error on average. Therefore, it is valuable for providing a fast, credible, and physics-based method for the prediction of flank tool wear in laser-assisted milling of various materials. Through sensitivity analysis, the model is able to guide the selection of cutting and laser parameters when the flank tool wear is the main concern.

Dynamic simplified PCM models for the pipe-encapsulated PCM wall system for self-activated heat removal

The energy efficiency of traditional PCM wall is low in summer since the PCM storing heat in the daytime will become a secondary heat-source and release the heat into the room again at night. In this paper, a novel pipe-encapsulated PCM wall system for self-activated heat removal is proposed. It integrates PCM, nocturnal radiation cooling and gravity heat-pipe technology, and can realize automatic heat insulation and self-activated removal for buildings. Three simplified models for pipe-encapsulated PCM are developed to predict its thermal characteristics. Model Parameters are determined and identified by using genetic algorithm. The pipe-encapsulated PCM is prepared by RT28 and expanded graphite. An experiment setup is established for model validation. Results shows that the 4R2C PCM model are preferable since the identified parameters are relatively less and the accuracy is also acceptable. Furthermore, a simple application about pipe-encapsulated PCM wall is proposed based on the coupled wall model with 4R2C PCM model. Compared with conventional wall, the internal surface accumulated heat transfer of the pipe-encapsulated PCM wall with night active heat removal in 7 days can be reduced by 74.5% in hot climate. It shows great application potential for energy-saving in buildings.

Numerical modeling of ultrasound heating for the correction of viscous heating artifacts in soft tissue temperature measurements.

Measuring temperature during focused ultrasound (FUS) procedures is critical for characterization, calibration, and monitoring to ultimately ensure safety and efficacy. Despite the low cost and the high spatial and temporal resolutions of temperature measurements using thermocouples, the viscous heating (VH) artifact at the thermocouple-tissue interface requires reading corrections for correct thermometric analysis. In this study, a simulation pipeline is proposed to correct the VH artifact arising from temperature measurements using thermocouples in FUS fields. The numerical model consists of simulating a primary source of heating due to ultrasound absorption and a secondary source of heating from viscous forces generated by the thermocouple in the FUS field. Our numerical validation found that up to 90% of the measured temperature rise was due to VH effects. Experimental temperature measurements were performed using thermocouples embedded in fresh chicken breast samples. Temperature corrections were demonstrated for single high-intensity FUS pulses at 3.1 MHz and for multiple pulses (3.1 MHz, 100 Hz, and 500 Hz pulse repetition frequency). The VH accumulated during sonications and produced a temperature increase of 3.1 °C and 15.3 °C for the single and multiple pulse sequences, respectively. The methodology presented here enables the decoupling of the temperature increase generated by absorption and VH. Thus, more reliable temperature measurements can be extracted from thermocouple measurements by correcting for VH.