Water Circuit Research Articles

Diamond film thermistors for dental vitality assessment

In this study, we have demonstrated, for the first time, the use of diamond film thermistors for dental vitality assessment. Thermally sensitive boron-doped diamond films were grown by hot-filament CVD on Si3N4 ceramic substrates, and their thermal sensitivity (β) in the 30–50 °C range was optimized using the Taguchi methodology. This analysis facilitated a comprehensive investigation into the effects of argon flow, gas pressure, CH4/H2 ratio, and the distance between the sample and heated filaments on the films' microstructure, growth-rate (GR), crystalline quality, and β. Additionally, we introduced an empirical parameter (Y), defined as the ratio of β to electrical resistance.Using optimized CVD parameters, we fabricated a fully functional diamond thermistor with a thermal sensitivity of 1435 K, which was then used in dental vitality assessment tests. These tests were conducted on a specialized stand featuring two closed water circuits, allowing the tooth to be cooled to temperatures as low as 10 °C and heated up to 40 °C. The heating response times of our diamond thermistor (DT) and a standard, metal-oxide-based commercial thermistor (CT) were comparable, but the diamond sensor exhibited a broader temperature detection range. Specifically, the DT was able to detect tooth temperatures within the range of 18 °C to 35 °C, whereas the CT was limited to a narrower range of 22 °C to 32 °C. Additionally, the cooling response time for the DT was significantly shorter (190 s) compared to the 260 s required for the CT. These findings highlight the potential of planar diamond thermistors for applications in endodontic medicine, enabling more accurate assessments of dental vitality.

Experimental Center El Remanso ECER in Choachi-Colombia. A Laboratory Eco-Village to Learn and Co-build a Circular Learning

AbstractThe purpose of this article was to show the progress in the implementation of an Eco-Village that incorporated elements of bioconstruction with the use of bamboo-guadua cane framed in a circular design and integrated planning approaches for the increasing resilience in an area of high seismic risk in the Colombian Andes Mountains. Likewise, it included energy transition elements advancing towards decarbonization with the use of solar panels for electricity generation and water heating. At the same time, it integrated clean production linked to regenerative agriculture and circular bioeconomy using closed water circuits from bioprospection purification processes in internal treatment plants, equally, waterless toilets that allow the use of human waste as an input for composting and urine mixed with water for nitrogen fixation in permaculture gardens. Likewise, Experimental Center El Remanso ECER has allowed the application of Interdisciplinary education related to Ecological Engineering Education. The project is framed in the concepts and theories of bioeconomy and degrowth (Georgescu-Roegen, Latouche). An exploratory qualitative methodology was considered based on the participatory action research PAR proposals of Fals Borda. In addition to, the meeting with the traditional knowledge of the indigenous people and the peasant communities of the area in the production and cooking of food and the recovery of soils and ecosystems, as well as, the implementation of associativity processes related to the design and execution of tourist routes. As result of the research, the importance of co-creation, respect for ancestral knowledgement and the dialogue of knowledges are recognized, among others. The used of the small sample size of the different information access instruments were recognized as a limitation in the research. However, future actions linked to the results of the implementation of the PAR are been planned.

Reforming Natural Gas for CO2 Pre-Combustion Capture in Trinary Cycle Power Plant

Today, most of the world’s electric energy is generated by burning hydrocarbon fuels, which causes significant emissions of harmful substances into the atmosphere by thermal power plants. In world practice, flue gas cleaning systems for removing nitrogen oxides, sulfur, and ash are successfully used at power facilities but reducing carbon dioxide emissions at thermal power plants is still difficult for technical and economic reasons. Thus, the introduction of carbon dioxide capture systems at modern power plants is accompanied by a decrease in net efficiency by 8–12%, which determines the high relevance of developing methods for increasing the energy efficiency of modern environmentally friendly power units. This paper presents the results of the development and study of the process flow charts of binary and trinary combined-cycle gas turbines with minimal emissions of harmful substances into the atmosphere. This research revealed that the net efficiency rate of a binary CCGT with integrated post-combustion technology capture is 39.10%; for a binary CCGT with integrated pre-combustion technology capture it is 40.26%; a trinary CCGT with integrated post-combustion technology capture is 40.35%; and for a trinary combined-cycle gas turbine with integrated pre-combustion technology capture it is 41.62%. The highest efficiency of a trinary CCGT with integrated pre-combustion technology capture is due to a reduction in the energy costs for carbon dioxide capture by 5.67 MW—compared to combined-cycle plants with integrated post-combustion technology capture—as well as an increase in the efficiency of the steam–water circuit of the combined-cycle plant by 3.09% relative to binary cycles.

Integrating double-labeling HCR-FISH into a multidisciplinary pipeline for biofouling assessment on austenitic stainless steel in brackish seawater circuit

This study modified and integrated a bioimaging method of hybridization chain reaction fluorescence in situ hybridization (HCR-FISH) into a pipeline for assessing biofouling on stainless steel (SS). A modified protocol of double-labeling HCR-FISH was directly applied to two surface types of SS grade EN 1.4404 to detect localized bacteria and sulfate-reducing bacteria (SRB) by targeting bacterial 16 S rRNA genes and dissimilatory sulfite reductase (dsrB) genes, respectively. The protocol was first validated using microbial pure cultures and materials before being integrated into a biofouling assessment pipeline of SS in a laboratory-scale brackish water circuit, incorporating electrochemical, surface, and molecular biology characterization analyses. The double-labeling HCR-FISH improved bioimaging of surface biofilm morphology and microbial distribution, surpassing monochrome staining methods. This method was compatible and complemented other microscopy techniques and molecular biological analyses, providing additional insights into the biofilms and deposits on the alloy surfaces. The implemented assessment pipeline for biofouling determination frequently detected the ennoblement phenomenon in the evolution of marine biofilm on SS surfaces. However, within the experimental timeframe, microbial activities in the brackish seawater circuit did not flourish significantly, resulting in minimal impact on the steel material. Additionally, surface type and roughness may correlate with microbial adhesion, biofilm growth, and the deformation of passivation layers in SS. Despite abundant sessile bacteria, particularly opportunistic microorganisms, on the steel surfaces, no direct correlations with biodeterioration phenomena or influences of surface roughness of an alloy and the presence of biofilm were conclusively established.

Calcium Carbonate Formation in Groundwater-Supplied Drinking Water Systems: Role of CO2 Degassing Rate and Scaling Indices Applicability

CaCO3 precipitation is a ubiquitous and vital process with far-reaching implications for various natural systems. In drinking water supply networks, it creates malfunctions in the system, especially by pipes clogging. This is a common problem in Tunisia, particularly for systems supplied with groundwater. This work attempts to highlight the effect of dissolved CO2 degassing kinetics and determine the most reliable scaling index to predict scaling. For this, a diagnosis of two drinking water circuits is followed by a laboratory study. Results of the field study show that the network scaling is controlled by the dissolved CO2 content, which is significantly affected by the water/atmospheric air contact. The scale formed is mainly CaCO3–calcite. A laboratory-scale simulation of the natural phenomenon using an experimental setup of the fast-controlled precipitation method (FCP) was performed. The result shows that a low CO2 content is a necessary condition for a supersaturated system regarding calcite but not sufficient for precipitation to take place. The precipitation can occur at very low supersaturations if time is allowed for stable nuclei to form, explaining the scaling of drinking water networks. The fundamental and applied study of the scaling indices shows that the Ryznar stability index (RSI) is the most adaptable index for predicting scale formation.

Developing an innovative corrosion and scaling index for industrial cooling water using artificial intelligence

The present study developed an intelligent model to predict the corrosion and scaling potential (CSP) of industrial cooling water circuits using artificial intelligence (AI) techniques. AI techniques have attracted a lot of attention due to the high accuracy and speed of calculations, as well as possible analysis of large datasets. The study analyzed nine years of data on cooling water quality parameters, including pH, alkalinity, hardness, dissolved solids, chloride, turbidity, suspended solids, and iron, from electric arc furnaces at the Khuzestan Steel Company. Multiple linear regression (MLR), multiple nonlinear regression (MNLR), and multi-layer perceptron neural network (ANN-MLP) models were applied to predict CSP. The ANN-MLP model achieved the best performance with an R2 of 0.75, Mean Absolute Error of 0.34, and Mean Squared Error of 0.35, demonstrating that neural networks can effectively predict CSP in industrial cooling water. The results also showed that total hardness and chloride have the greatest impact on CSP in the circulating water circuits.

Study on the Design of Valve Base Insulation and Power Supply Transformer for High-Voltage DC Circuit Breaker

Abstract High-voltage DC circuit breaker is a key piece of equipment to building DC power grids. DC circuit breakers need to support and isolate from high voltage to ground through valve-based equipment and use valve-based power supply transformer to continuously supply energy to high potential components, the electrical performance of these two equipment determines whether DC circuit breakers and DC networks can be operated safely and reliably. For this reason, this paper carries out the research on the insulation capability of the valve base and the performance of the power supply transformer, such as the design and simulation of electric and thermal fields, as well as the test program. Firstly, the insulation design and simulation study of the valve base as a whole is carried out, and the design optimization of the equipotential scheme of the top homogeneous tubular bus, diagonal pull insulator and hydroelectric pole is completed. Secondly, the design and simulation verification of the thermal field distribution of the energy-supply transformer, the overvoltage between the ends of the output windings and the optimization scheme, and the short-circuit impedance were carried out. Finally, the insulation performance of the valve base, the temperature rise of the energy supply transformer, the overvoltage simulation of the output winding and the short-circuit characteristics were tested. The results show that: after optimization, the maximum field strength of the homogenizer is 2.3kV/mm, and the overall maximum field strength of the valve base is 2.61 kV/mm on the diagonal insulator, and there is no pressure difference between the water circuit and the fittings using the three-pin vertically distributed hydropower electrode scheme; the temperature rise of the supply transformer in the simulation and the actual measurement is 27K and less than 30K; by means of the parallel connection of the MOV, the overvoltage of the output winding of the power supply transformer under voltage impulse is effectively reduced to -1.8kV; the measured short-circuit impedance of the power supply transformer is 69.5%. The optimized design of DC circuit breaker valve base and power supply transformer can operate safely, and effectively support the construction of DC circuit breaker and DC power network.

Impact of nuclear heating distribution on the structural behavior of ITER first wall panel 11

The ITER blanket system safeguards the Tokamak's Vacuum Vessel and ex-vessel components from thermal and nuclear loads induced by the plasma. It comprises two parts: the First Wall panel facing the plasma and the Shield Block that provides the bulk of the shielding. The First Wall panels consist of Beryllium tiles on a CuCrZr layer, supported by stainless-steel structures which are cooled using a pressurized water circuit at 40 bar with an inlet temperature of 70 °C.Fusion for Energy has updated the thermal and mechanical analyses of ITER First Wall Panel 11 in preparation for the serial manufacturing. The panel will face heat flux up to 2 MW/m2 from plasma radiation, in addition to the volumetric nuclear heating, and the electromagnetic loads. A model with an enhanced detailed 3D geometry and heterogeneous materials indicates a 25% reduction of the deposited heating compared to the previous 2D model, from 625.4 kW (2D) to 455.4 kW (3D).The study embraces numerous thermal and mechanical analyses using Ansys software v19.2, incorporating 2D and 3D nuclear heating data. Responses are then compared and thus the possible impact of the two distributions on the thermal and mechanical behavior of the Fist Wall Panel 11 is assessed.

Research on Metal Corrosion Behaviour of Indirect Air-cooled Circulating Water System

Abstract The indirect air cooling system of an air-cooled power plant consists of a surface condenser and an aluminum radiator. The radiator is usually made of 1050A pure aluminum, and the circulating water pipe connecting the radiator is made of Q235B carbon steel. This article simulates and controls typical water quality parameters such as dissolved oxygen and pH value in indirect air cooling systems using a self-designed simulation device, and studies the influence of various water quality parameters on material corrosion behavior in intercooled circulating water systems when aluminum and carbon steel coexist. The results indicate that factors such as dissolved oxygen, conductivity, pH value, temperature, and redox potential can all affect the corrosion rate of carbon steel and aluminum materials; The increase in temperature and dissolved oxygen leads to an increase in corrosion rate; The main way carbon steel corrodes the system is by consuming dissolved oxygen; The corrosion behaviour in the water circuit will lead to an overall decrease in pH value. In the presence of multiple metals, the influence of iron ions in the solution significantly increases the corrosion rate of aluminum.

Using HFMEA to Reduce the Number of Colonies in the Water of Hemodialysis Room

<p>運用HFMEA手法降低血液透析室水處理之菌落數<br />國內血液透析中心發生多起透析用水處理不當導致的醫療疏失，讓醫病關係產生緊張及不信任感。本單位2018年04月至09月因透析液送檢不合格率為0.2%，故成立專案小組藉由醫療失效模式效應分析，檢視透析用水處理流程。發現問題有：漂白水濃度不足、漂白水靜置時間不足、透析機無自動開機沖洗、班間沖洗時間不足、透析機消毒時未吸取消毒液、透析機移動重新接水路未執行沖洗、透析用水採檢技術流程知識不足等問題，其改善措施為：修訂水處理系統消毒規範、修訂透析機消毒規範、修訂透析用水採檢流程。對策實施後，不合格率由0.2％降至為0％，高為險因子由10項降低為0項。藉此次專案讓人員瞭解HFMEA是著重於系統分析，可預防錯誤發生進而提升醫療安全。</p> <p> </p><p>Many cases of medical negligence caused by improper treatment of dialysis water occurred in domestic hemodialysis centers, which caused tension and mistrust between doctors and patients. From April to September 2018, the unqualified rate of dialysate was 0.2% in our hemodialysis room. Therefore, a task force team was set up to examine the dialysis water treatment process through the analysis of medical failure mode effects. We found problems that include: insufficient concentration of bleach water, insufficient standing time of bleach water, no automatic start-up flushing of the dialysis machine, insufficient flushing time between shifts, no antiseptic solution was absorbed during the disinfection of the dialysis machine, flushing was not performed when the dialysis machine was moved and reconnected to the water circuit and insufficient knowledge of the technical process of sampling of dialysis water. The measures of improvement are revising the disinfection specification of water treatment system, revising the disinfection specification of dialysis machine, and revising the sampling process of dialysis water. After the implementation of the countermeasures, the unqualified rate was reduced from 0.2% to 0%, and the high risk factors were reduced from 10 to 0. Through this project, personnel can understand that HFMEA focuses on system analysis, which can prevent errors and improve medical safety.</p> <p> </p>

Control of Carbon Dioxide Bivalent Heat Pump on Heating of Buildings

The scheme of a bivalent heat pump (BHP) is considered, using both the heat of the water from the return network and the heat of the outside air as low-potential heat sources (LPH). The aim of the work is to create a BHP circuit that provides functioning at the variable heat load temperature. The goal was achieved by solving the following problems: analysis of methods of synthesis of BHP circuits, analysis of circuit operation under random disturbances and development of the automatic control systems for BHP. The most significant result of the work is: a heat pump circuit that can operate at variable pressures of the evaporator and the gas cooler. The next significant result is, for bivalent heat pumps intended for operation in heat supply systems with qualitative and qualitative-quantitative laws of thermal control, the introduction into the heat pump circuit of a heat exchanger installed in the return water circuit of the secondary building and cooled by outside air, as well as two control valves installed in series between the gas cooler and the evaporator, the first valve installed along the refrigerant flow being controlled by a signal based on the pressure difference between the outlet of the gas cooler and the separation vessel between the evaporator and the gas cooler, and the second by pressure in front of the evaporator. The significance of the obtained results lies in the increase of the COP of the heat pump, due to the increase of heat transfer in the gas cooler circuit. The HHP circuit differs from the known ones in that it uses two control valves and the heat exchanger for additional cooling of the return water of the BHP heated building.

Комплексные решения по управлению хвостовым хозяйством на Усольском калийном комбинате

Introduction. At enterprises engaged in the extraction and processing of mineral raw materials, the volume of production waste is usually much higher than the volume of a commercial product. At the same time, there is a tendency to decrease the metal content in ores while increasing the volume of waste rock extracted when accessing ores. According to various estimates, the annual volume of waste from mining enterprises is 7 billion tons per year. The proportion of waste (tailings) in some copper-containing ores can reach 98 % or higher. Gold mining enterprises process ores in which tailings amount to 99.9 % and which contain only a few grams of gold. This trend will continue, as the enterprises of the mineral processing industry have to increase the volume of processed products. Materials and methods. Tailings processing technology solutions include equipment and services that can be used in almost any tailings farm, while tailings thickening and paste thickening can be used. Just as in the case of surface tailings management solutions, the development of solutions for underground workings begins with consideration of the available storage space underground. Post and dry storage technologies combined with closed water circuits represent the best options available for saving water in processing plants. In traditional tailings systems, the source of process water is natural sources or groundwater from mine drainage. Results. The use of sludge dewatering technology has significant advantages in handling excess brines, because it allows you to separate the mother liquor, return it to the technology and thereby prevent discharge to the sludge storage. To enhance the effect of sludge dewatering, it is necessary to limit the supply of fresh water to the technological process beyond the level of irretrievable losses (for example, evaporation into the atmosphere) by using a mother liquor or recycled brine instead of water. Discussion. liquid phase entering the sludge storage, increase the efficiency of hydraulic transport, and increase the service life of tailings facilities. Scientific works confirm the possibility of using filtered sludge from potash factories as a meliorant for agriculture and restoration of forest soils after fires. When implementing integrated tailings management, it is necessary to take into account the existing conditions and limitations of the site, the requirements of the technological process of a particular enterprise. Conclusion. The article presents the results of research on the dehydration of sludge of potassium salts. It has been established that the sludge dewatering technology significantly reduces the volume of sludge entering the sludge storage, which will increase the efficiency of hydraulic transport, increase the service life of tailings facilities. Resume. The use of sludge dewatering technology can significantly improve the efficiency of the processing plant. The development of sludge dewatering technology will require a number of research projects on transportation, storage and logistics of meliorant.

Investigation of water heating efficiency in cavitation mode at initial stage of grain molasses preparation

BACKGROUND: Grain molasses are a valuable source of digestible protein and feed sugar for farm animals. At the initial stage of production of this feed mixture, the existing devices and water heating schemes are not effective enough. In this connection, a new device for accelerated heating of passive-type water has been developed.
 AIMS: evaluation of the effectiveness of the cavitator for heating water in the plant for the production of grain molasses.
 MATERIALS AND METHODS: for conducting studies, a cavitator made in the form of a cone with petals, the angle of the solution of which is 168ʹ, is installed in a glass pipe of the injection branch of the water circuit of the plant for the preparation of grain molasses. During the experiments, the petals were installed in the pipe straight or bent 15. Under laboratory conditions, a comparative experiment was carried out to heat water with a volume of 50 liters, starting from its temperature of 20C and through each degree to 30C, both with and without a cavitator. The process efficiency criteria were: time and specific energy consumption of water heating.
 RESULTS: as a result of the conducted studies, the values of the criteria for the efficiency of the water heating process using a cavitatora and without it are established. Linear dependence of water temperature on heating time is obtained. It has been shown that the created cavitation effect behind the base of the cone is not stable, but still more intense behind the cone with straight petals. It is noted that the coefficient of hydraulic resistance for a cavitator with bent by 15 lobes is 10% greater than with straight ones.
 CONCLUSIONS: use of a cavitatora when heating water at the initial stage of preparing grain molasses increases efficiency of the process by 20%.

Research on Equivalent Circuit Model of HVDC Valve and Calculation of Thyristor Junction Temperature

For the difference of thyristor junction temperature at all levels in the transducer valve assembly in the series water circuit, an equivalent model of thyristor junction temperature calculation for the valve assembly is established, and PLECS simulation software is used to simulate and solve the junction temperature at all levels of the thyristor and check the junction temperature of the thyristor from the highest temperature of the measured radiator surface, and the results of the junction temperature checking show that the equivalent model of thyristor junction temperature calculation for the valve assembly has a high accuracy.

Scheme design and flow performance analysis of double-bits combination wire-line coring technology for seafloor drill

In order to meet the requirement of high-quality samples for evaluating marine mineral resources reserves, a double-bits combination wire line coring scheme for seafloor drill is proposed. The Bernoulli math model reflecting the drilling fluid pressure variation inside the drilling tool is established. The influence of the drilling tool’s water circuit parameters on the drilling fluid pressure variation is clarified. The drilling fluid’s flow performance during the drilling process is analyzed. The drilling performance of this scheme is tested through engineering application. The application results indicate that: When the inner tube bit’s water channel cross-section A1 reaches 30mm2, A2 reaches 20mm2 and the A3 reaches 20mm2, the drilling fluid pressure ΔP in the drilling tool tends to stabilize. The influence of PVC tube outside diameter d8 on drilling fluid pressure ΔP is small within the allowable design range of 62–65mm. The simulation results show a high-speed area in the first section of the water channel in the inner tube bit. Selecting pump displacement in 50–90 L/min has more engineering application value. The engineering application in complex seabed strata shows that the average core sampling rate is more than 85% within the pump displacement of 50-90 L/min and rotation speed of 350–450 r/min.

Amphoteric dry strength chemistry approach to deal with low-quality fiber and difficult wet-end chemistry conditions in the Asian and North American markets

With Japan’s high recycling rates and low access to fresh fiber sources, reaching strength targets in manufacturing packaging materials is a challenge. Declining quality of recycled fiber and minimal freshwater consumption results in difficult wet-end chemistry conditions in terms of high conductivity and elevated levels of dissolved and colloidal substances (DCS). These trends are somewhat typical of other Asian regions. Due to global trade, Asian packaging materials have become a part of the North American (NA) raw material pool. The gradual closing of mill water circuits for fresh water and energy savings results in more difficult wet-end chemistry conditions experienced in North America. China’s ban on the import of mixed paper and the consequent ban on all waste-paper imports triggered a significant price drop in recycled raw material, resulting in plans for increased manufacturing capacity in North America. Between increased demand, decreasing fiber quality, and movement towards more closed white water systems associated with packaging grade paperboard (even a virgin fiber mill uses a fair amount of recycled fiber), new methods to overcome strength reduction in raw materials must be proactively considered for North America. Reviewing the strategies currently used in the Asian industry regarding strength development is an excellent starting place for NA producers. A clear difference between Asian and NA wet-end chemistry is the dominant position of amphoteric dry strength agents. This paper reviews the fundamentals of dry strength development that explain the trend towards the increased application of amphoteric dry strength technology for poor-quality fiber and highly contaminated water circuits in Asian markets. This paper discusses the development and application performance of the novel 4th generation amphoteric polyacrylamide (AmPAM) dry strength technology, based on selected laboratory and mill case studies.

Integrated Design and Fabrication of Pneumatic Soft Robot Actuators in a Single Casting Step.

Bio-inspired soft robots have already shown the ability to handle uncertainty and adapt to unstructured environments. However, their availability is partially restricted by time-consuming, costly, and highly supervised design-fabrication processes, often based on resource-intensive iterative workflows. Here, we propose an integrated approach targeting the design and fabrication of pneumatic soft actuators in a single casting step. Molds and sacrificial water-soluble hollow cores are printed using fused filament fabrication. A heated water circuit accelerates the dissolution of the core's material and guarantees its complete removal from the actuator walls, while the actuator's mechanical operability is defined through finite element analysis. This enables the fabrication of actuators with non-uniform cross-sections under minimal supervision, thereby reducing the number of iterations necessary during the design and fabrication processes. Three actuators capable of bending and linear motion were designed, fabricated, integrated, and demonstrated as 3 different bio-inspired soft robots, an earthworm-inspired robot, a 4-legged robot, and a robotic gripper. We demonstrate the availability, versatility, and effectiveness of the proposed methods, contributing to accelerating the design and fabrication of soft robots. This study represents a step toward increasing the accessibility of soft robots to people at a lower cost.

Design of Conformal Cooling System with Lattice-structure of Mold Based on 3D Printing

The conformal cooling water circuit manufactured by using metal 3D printing SLM technology has significant advantages, compared to the straight drilling cooling water circuit, but there is still a problem of large temperature differences in local mold positions. Based on a circular cross-section spiral-shaped waterway, this article proposes a design that replaces a circular cross-section single helix with a runway-shaped double helix structure and sets a lattice structure in areas with large temperature differences. Finally, Moldflow is used to simulate the cooling effects of the two cooling forms. The results show that the lattice structure can significantly improve the phenomenon of uneven cooling, and the surface temperature difference of the mold has been improved by 41%. Compared to the circular section, the runway-shaped section has a better cooling effect, better temperature distribution, and more uniform cooling.

TRNSYS MODEL OF THE COMBI BOILER DOMESTIC HOT WATER CIRCUIT WITH A FOCUS ON THE PARAMETER DEFINITION OF THE PLATE HEAT EXCHANGER

Combi boilers used for both space and domestic hot water heating are one of the common household appliances. Modelling the domestic hot water circuit of a combi boiler for the preliminary evaluation of the laboratory testing is of crucial importance since it decreases the time, cost, and energy spent on the trials. There are various modelling approaches established by the authors of this paper. Domestic hot water circuit of the appliance is modelled previously making use of the Transient System Simulation Tool (TRNSYS 18) and a good agreement is achieved with the experimental and numerical data for the economic mode simulations. The drawback of the current TRNSYS model is the dependence on the experimental data for some of the parameter definitions of the components selected from the TRNSYS library, i.e. UA (multiplication of the overall heat transfer coefficient and the heat transfer area) input of the plate heat exchanger and heat retention effect of the heat cell block. In this paper, a constant value is assigned to the parameter definition of UA instead of a time dependent varied profile. Mean absolute errors covering the steady-state and transient operating regions for the domestic hot water inlet and outlet temperature difference in economic mode simulations stay nearly the same around 0,46°C, 0,82°C, and 0,53°C for 5 l/min, 7 l/min, and 8,7 l/min, respectively, under constant and variable UA approaches. Comfort operating scheme model is established with a couple of experimental data as of the principal application of the constant UA approach. Mean absolute error of the overall domestic hot water inlet and outlet temperature difference profile decreases to 0,5°C in the comfort mode simulation.

Evolving from an indirect evaporative cooling system to a radiant-capacitive heating and cooling system for low-mass buildings

The study shows the development of a novel passive cooling system parting from previous experience gathered with an Indirect Evaporative Passive Cooling System (IEPCS), originally employed in a low-income dwelling located in the hot-humid climate of Maracaibo, Venezuela. Using the design thinking approach, we optimized the original passive cooling system so as to curb some limitations observed in the IEPCS, and developed a novel passive cooling and heating system more suitable to refurbishment schemes of low-mass dwellings in tropical areas. We present comparative results from test runs in small-sized test cells for the subtropical climatic conditions of Curitiba, Brazil. The hydronic system operates with water circuits to and fro a thermal storage unit, a sky radiator/solar collector to radiant-capacitive modules indoors. Results showed that while both the roof-pond system and the radiative cooling system with indoor capacitive module provide stability to the indoor thermal environment, a somewhat greater thermal amplitude is observed in the latter, which is partly due to the difference in thermal mass between the two systems. Cooling output of the novel system was somewhat lower than that of an indirect evaporative system and dependent on atmospheric exposure conditions of the sky radiator. Heating output is given as a function of pumping duration. Cooling potential reached about 78 % of that of the roof-pond module, for test conditions with nocturnal sky radiative cooling and no water circulation from the storage tank to the interior during the day.