Total Heat Consumption Research Articles

Simulation of the work of glass furnaces with the purpose of searching for reserves and increase their efficiency

The object of research is the operation of a glass furnace. The work involved modeling the operation of a glass furnace by changing the technical and economic indicators of its operation in order to optimize the technological processes of manufacturing glass products, increase the energy efficiency of the process, and reduce the ecological burden on the environment. Glass furnaces are complex heat engineering units that require a large amount of energy to operate. Therefore, increasing their effectiveness is the main task of our research. In the work, computer modeling of thermal processes in the furnace was carried out, heat balances were calculated and analyzed, and the performance of the furnace was analyzed after changing and improving the technological regimes of combustion processes, glass boiling and furnace construction. Studies have shown that in order to increase the technical and economic performance of glass furnaces, it is advisable to conduct additional thermal insulation of the furnace enclosures. The thermal insulation of the vault increases the efficiency of the furnace by 2–3 %, and the thermal insulation of the remaining areas of the furnace in total allows to increase the efficiency of the heating unit up to 3 %. Such measures improve the sanitary and technical working conditions of the staff in the machine-bath shop. Studies have shown that additional heating of the air used for burning fuel significantly increases the efficiency of the furnace. Thus, an increase in air temperature by 100 °C increases the efficiency of the furnace by approximately 2.5 %. However, such a measure is possible with a corresponding increase in the volume of regenerator nozzles. A significant increase in the efficiency of the furnace was achieved when additional electric heating was installed. This allows to reduce the total energy costs, and at the same time, the introduction of every 10 % of additional electric heating increases the efficiency of the furnace by up to 3 % and improves the quality of the glass mass. Such additional heating can be recommended in the amount of 20–30 % of the total heat consumption for the operation of the furnace. The analysis of the obtained results showed a fairly good convergence of the results, which indicates the acceptable adequacy of the models. The obtained process simulation results allow choosing the optimal design and operation parameters of the glass furnace. The results of the work can be used in practice for the design of efficient glass furnaces of various purposes and performance.

Integrated heat dissipation mechanism design of electronic equipment cabinet based on flow and sound analysis

The electronic equipment cabinet is the main bearing platform of radar back equipment, normally using a forced convection cooling form. With the continuous increase of radar function and processing capacity, the total heat consumption of electronic equipment is getting higher and higher, and the fan speed is constantly increasing. Besides the noise of electronic equipment cabinet shows a trend of gradually increasing. To reduce cabinet noise from the source, this paper presents three structural forms of integrated heat dissipation mechanism, and uses FloEFD fluid heat transfer analysis software and COMSOL acoustic module to analyze the cabinet flow field and the cabinet sound field respectively. By comparing the cabinet noise characteristics under different structural forms, the analysis results show that the noise reduction effect of bilateral air duct structure is best.

Energy Efficiency State Identification for Cogeneration Units Based on Benchmark Value

In China, cogeneration units predominantly employ a flexible operation mechanism. However, it is possible that this could lead to a decline in performance and an increase in energy consumption. This paper introduces a methodology that utilizes the data mining technique to ascertain the benchmark value section of the energy efficiency status index for cogeneration units. The equal interval division method is utilized for the purpose of categorizing the operating conditions. The Gaussian mixture model is utilized to ascertain the benchmark value section in relation to the fluctuating operating conditions by estimating the probability of historical data. The methodology is verified by utilizing historical data from a functioning cogeneration unit. The findings suggest that the unit’s total heat consumption can be decreased by 32.5–50 kJ·(kW·h)−1 when compared to the design-based approach.

Processing of Manure in Biogas Plants

Biogas obtained from agricultural waste is becoming increasingly important as a renewable resource. Biogas can be obtained by biological and thermochemical methods. The first is the decomposi­tion of organic substances without air access due to the fermentation process, which takes place at a temperature of 30-40 degrees Celsius for «clean» waste (for example, microbiological industry) or 55-60 degrees Celsius for animal waste and urban wastewater. As a result of decomposition, biogas and a number of valuable components (nitrogen, phosphorus, potassium oxide) are formed, from which a highly effective organo-biofertilizer is prepared. (Research purpose) The research purpose is increasing the uniformity of the temperature field over the volume of the bioreactor to intensify the thermophilic process of anaerobic processing, increasing the yield of biogas and improvement of the quality of the biofertilizer. (Materials and methods) For the purpose of laboratory experiments, droppings from the poultry house of the peasant farm “Khemzet” of the Kabardino-Balkarian Republic were used with the analysis performed in the laboratory of the agrochemical service “Kabardino-Balkarian”. The total daily heat consumption and the capacity of the heat exchanger-agitator were determined using mathematical modeling and the laws of thermodynamics. (Results and discussion) The contents of the methane tank were heated by a heat exchanger using a coolant, and mixing was carried out using a mechanical stirrer combined into one heat exchanger–stirrer unit powered by an electric motor. It was shown that during the thermophilic process, more intensive and deeper fermentation of precipitation occurs, which contributes to a decrease in the volume of the methane tank, more effective destruction of helminths and weed seeds. It was found that during thermophilic fermentation, a greater amount of heat is needed to heat the sediment in the methane tank, 12-15 days are enough to disinfect the mass. (Conclusions) It was found that the optimal values of the temperature of the substrate processing process are 56.6 degrees Celsius; the mixing time is 17 minutes, the number of revolutions of the heat exchanger-agitator is 7.5 revolutions per minute. Chemical analysis of the obtained organo-biofertilizers was carried out.

Performance analysis and optimization of a coupled open and close liquid desiccant sorption system using LiCl solution

The efficient utilization of low-grade heat for air conditioning has been a topic of world concern, especially for low-grade heat below 80℃. In this study, a novel coupled open and close liquid desiccant sorption system driven by 70 ∼ 80℃ low-grade heat is proposed. This system employs a generator to provide strong solution for both the dehumidifier and absorber, achieving the air temperature and humidity independent control to reduce driving temperature and enhance system performance. A mathematical model is developed to simulate the proposed new system, and a comparative analysis is conducted with a traditional combined absorption refrigeration with liquid desiccant dehumidification system using LiCl solution. It is found that the COP of the new system is 0.76, which is higher than 0.65 of the traditional system when the hot water temperature is 75℃, the reason is that the new system avoids the sensible heat consumption of regenerated air which accounts for 17% of the total heat consumption in the traditional system. Furthermore, it is observed that the outlet concentration difference between the absorber and dehumidifier exists in the new system. The cycle is optimized to improve the concentration difference, leading to a 5.5% increase in the COP. After that, economic performance analysis shows a payback period of 2.65 years for a 150 kW cooling capacity system, with a reduction of 86.6 tons of CO2 emissions per year due to the decrease in power consumption.

Thermodynamic modelling of integrated carbon capture and utilisation process with CaO-based sorbents in a fixed-bed reactor

The global emission of CO2 through fossil fuel combustion is still increasing, which is a major challenge for the international community. An integrated carbon capture and utilisation (ICCU) process with a CaO-based sorbent is a promising alternative to effectively reduce emissions. In this work, a comparative thermodynamic analysis of two CaO-based sorbents (commercial and sol-gel CaO) was performed for one cycle of ICCU. In addition, the influence of temperature was investigated from 600 to 750 °C in terms of the degree of CO2 conversion. Thermodynamic calculations were based on the actual gas composition and developed model, where heat consumption and entropy generation were calculated. The results indicate that the degree of CO2 conversion decreased from 84.6 to 41.2% and from 84.1 to 62.4% for the sol-gel and commercial material, respectively, as the temperatures increased. Furthermore, the total heat consumption during one cycle decreased with higher temperatures. The total amount of consumed heat decreased from 19.1 to 5.9 kJ/g and from 24.7 to 5.4 kJ/g for sol-gel and commercial CaO, respectively. Although commercial CaO always requires more heat during one cycle. Moreover, for both materials, the lowest generation of entropy was calculated at 650 °C with values of 9.5 and 10.1 J/g·K for the sol-gel and the commercial CaO, respectively. At all temperatures, the commercial CaO generated a greater entropy.

Evaluation of district heating patterns for Hungarian residential buildings: Case study of Budapest

The present study focuses on analysing the heat consumption of multifamily buildings. The study evaluates measured district heating consumption data in Budapest, Hungary. The examined 218 buildings were grouped into 11 building types based on their architectural characteristics and analysed separately. The study aims to answer the question: how the buildings' characteristics influence the energy demand of the buildings. In the buildings only the total energy consumption is measured, thus the domestic hot water energy demand was examined in the summer months, when there is no heating in the building. The domestic hot water heat loss was 37–54% of total heat consumption in the summer period. The specific total district heating consumption data [kWh/m3/day] has higher deviation in colder months. The length of heating period is 183 days in Hungary, however the average length of heating period was longer in the examined buildings and it was even longer in case of the uninsulated buildings. From the measured consumption data the energy signature curves were developed for each building type for both the insulated and uninsulated buildings separately and the results were compared and analysed in detail. The energy signature diagrams showed a significant gap between the insulated and uninsulated buildings’ total district heating consumption data in the heating period. Lines were fitted to the data and the slope of the lines fitted to uninsulated buildings’ data indicate higher decline for every building type. A separation method was also suggested to divide the data of heating and non-heating period if its term is unknown. The difference between the average slope values of the fitted lines were analysed compared to buildings’ characteristics. It aimed to examine if the consumption reduction is influenced by the buildings’ physical parameters. In conclusion, the buildings’ characteristics did not always influence the final results (e.g. domestic hot water heat loss). But uninsulated buildings tend to have longer heating periods and buildings with smaller cooling surface area per heated volume had a predominantly lower energy consumption reduction rate.

STUDY OF THE HEAT OF DEHYDRATION OF D–FRUCTOSE SOLUTION

The heat of evaporation of water is the main component of the consumption during the drying of bio raw materials. Its share in the consumption depends not only on the initial moisture content of the drying object. As our previous studies have shown, the state of water in the material affects the total heat consumption. The state of water is determined by its chemical composition and structure. Drying objects rich in sugars deserve special attention. Sugars have a high tendency to hydration, are concentrated in the juice and determine both the kinetics and heat of dehydration. The most reliable data on glucose and fructose hydration are analyzed and presented. Measurement of the specific heat of evaporation of water r from fructose solutions with an initial concentration of 12.5 wt. % was performed in the evaporation calorimeter. Continuous registration of changes in heat flows and mass of the sample was ensured during the measurement process. The dependence of the reduced specific heat of evaporation of water (R = r/rtab) on the concentration of fructose was obtained in the isothermal mode at 40, 60 and 80 °C. The presented curves reflect the thermal processes occurring in the solution during water removal. The processes are characterized by an endothermic period of dehydration and an exothermic period of simultaneous dehydration and spontaneous homogeneous crystallization of fructose. It was found that the change in the degree of hydration of fructose in solution from 12.5 to 5 mol/mol occurs with increasing, almost linear, specific heat consumption. Removal of water from the first coordination sphere, when the degree of hydration decreases to values <5, the increase in specific heat of evaporation is steeper and reaches the excess over the tabular values of heat of evaporation of pure water rtab by 6 – 7 %. The heat of spontaneous crystallization of fructose has a power greater than the power of endothermic heat consumption for dehydration, therefore, a general exothermic effect is recorded. It is shown that the measured specific heat of water evaporation increases with increasing concentration of solutions despite a decrease in the degree of hydration of fructose. It was established that water has a strong hydrogen bond with sugar in solutions in which the degree of hydration of fructose is less than ~5. Assumptions about strongly and weakly bound hydrated water in solutions of monosaccharides are substantiated.

Can heat pump heat storage system perform better for space heating in China’s primary schools? A field test and simulation analysis

The space heating system has a significant influence on the energy consumption and comfortable indoor environment for primary schools in China’s cold area. This study investigated the operational performance of heat pump systems in two primary schools. Results showed that the primary school buildings had high heating load at turn-on period every morning, which then quickly decreased when the students came to classroom. With this wide-range variation of heating load and unreasonable control strategy, the mismatch between heat source and heating demand happened very easily among the whole heating season. It then led to typical issues and poor energy efficiency of heat pump systems, including excessive space heating after school, low load ratio and frequent start-stop operation of heat pump systems, small water temperature difference and excessive water flow rate of water distribution system, etc. In allusion to those core issues, the heat pump heat storage system (HPHS) was raised for space heating in primary schools to decouple the heat supply side and the heat demand side. Then this study simulated and analyzed the operational performance of HPHS. Results showed that with reasonable control strategy, the excessive heat supply after school was effectively avoided to save almost 51% of the total heat consumption. Besides, the heat pumps could operate stably with almost full heating load for heat storage, thus reaching better energy performance with annual average COP of 5.13. Also the water distribution systems in the ground side, heat storage side and user side could reach better energy performance with high energy efficiency and reasonable water temperature difference among the heating season. Therefore, the HPHSs with reasonable control strategy could effectively solve those typical issues and are more suitable for primary schools.

Multi-Case Study on Environmental and Economic Benefits through Co-Burning Refuse-Derived Fuels and Sewage Sludge in Cement Industry.

The use of waste as an energy source in cement clinker production is a promising way to transition toward a circular economy and limit carbon dioxide (CO2) in the atmosphere. The cement industry is responsible for around 5% of global CO2 emissions. In this paper, the analysis of environmental and economic profits associated with the substitution of coal by two refuse-derived fuels (RDF) and sewage sludge (SS) in a cement kiln was presented. Differences in the fuel-related CO2 emissions were calculated for two-, three-, and four-component fuel blends based on the fuel consumption data, heating values, and the correspondent emission factors. The biogenic fraction content of 19% and 43% were measured in RDFs. The material balance of fuels with the assumed technological parameters of the cement clinker production installation (capacity of 6000 Mg per day and unit heat of 3.6 GJ) shows that the RDF heat substitution at the level of 90% allows for a saving of approximately 28.6 Mg per hour of coal, and to manage even approx. 40 Mg per hour of RDF. The increase in the share of SS in the total heat consumption to 6% contributed to reducing the actual emissions by 17 kg of CO2 per 1 Mg of clinker. Multilateral benefits due to the use of RDF in the cement plant were evident.

Development of the District Heating System on the Left Bank of the Daugava River in Riga

Abstract In Latvia, heat supply is provided in three different ways: using district heating (hereinafter – DH), local heating and individual heating systems. Heat energy consumption consists of heat energy consumption for heating, hot water and heat energy technological processes. The structure of DH consumers has not changed in recent years and the largest consumers of heat are households – 70 % of the total energy consumption. The district heating system accounts for approximately 29 % of the total consumption. There is also the so-called tertiary sector, which is made of municipal and state buildings with a minor total heat consumption of about 1 %. It should be noted that 65–70 % of energy is used for heating needs, and 30–35% for hot water preparation. In Latvia, heat of DH consumers is produced both in boiler houses (hereinafter – BHs) and cogeneration plants (hereinafter – CHPs). The latter also produce electricity. Over the past 10 years, the distribution of heat produced in BHs and CHPs has changed significantly. The heat supply of the Latvian energy sector is a system consisting of three main elements – heat source, transmission and distribution networks, and end consumer. Low efficiency of heat supply system elements creates risks to security of heat supply, resource sustainability and competitiveness. Increasing energy efficiency in the system as a whole, or in individual elements of the system, will promote the enhancement of the heat supply sector, while promoting economic growth as well. The research attempts to evaluate the energy efficiency of DH systems in the so-called left bank (hereinafter – LB) DH area (located on the left bank of the Daugava River in Riga).

Impact of energy efficiency and decarbonisation policies for buildings: A comparative assessment of Austria and Switzerland

Reducing heat demand and decarbonising heat supply are essential if countries have to meet net zero emission targets. This paper presents a comparative assessment of the impact of energy efficiency polices for heat demand reduction and heat decarbonisation in the buildings sector (2000–2017) in Austria (AT) and Switzerland (CH). It assesses the heat demand, heat supply, effect of different factors on changes in total heat consumption, impact of energy policies that provide public subsidies for heating and compares the effectiveness of different policies and measures. The assessment shows that renewable heat supply in residential buildings has to be increased by about 150 PJ (130% increase from 2017) in AT by 2040 and by 120 PJ (210%) in CH by 2050, which is challenging. Energy savings from improvements in energy efficiency from 2000 to 2017 are 83 PJ in AT and 97 PJ in CH, but these are largely offset by increase in activity and wealth effects thereby resulting in small changes in final heat consumption. The average (2014–2017) annual public subsidies for heating were about 2500 million Euros and 310 million CHF and contributed to 51% and 36% share of energy saving in AT and CH respectively. Both countries achieved similar energy savings, albeit following different policy approaches. Public subsidies for heating are an important policy instrument in AT but have lower cost effectiveness. On the other hand, CH minimised the use of public spending by deploying other policies and funding measures that leveraged private investment to achieve similar energy savings.

A Thermodynamic Method for the Estimation of Free Gas Proportion in Depressurization Production of Natural Gas Hydrate

Free gas saturation is one of the key factors that affect the overall production behaviors of hydrate reservoirs. For example, different free gas contents could alter the thermal response of hydrate reservoirs to the artificial stimulation and hence change the gas production performance. To investigate whether and how much the hydrate reservoir contains free gas, we proposed a thermodynamic method to calculate the total heat consumption of hydrate dissociation throughout gas production and assess the free gas proportion. Based on the monitoring data of the first offshore hydrate production in Japan, we calculated the total heat consumption and analyzed the contributions of heat convection, heat conduction, and sensible heat during the entire test. The calculation results showed that there is likely to be a certain amount of free gas in the hydrate reservoir in the Eastern Nankai Trough. In addition, the analysis of different heat sources revealed the critical thermodynamic phenomenon in which the reservoir sensible heat was the main source for enthalpy of hydrate dissociation, which consistently contributed more than 95% of the total heat supply during the 6-day production test. The results of this work may help upgrade the production strategy for natural gas hydrates.

Influence of low temperatures on heat balance in easily assembled premises of different types

The purpose of this work was to analyze the thermal balance of easily assembled premises of different types and sizes during the periods of low average daily temperatures. The research was conducted during the winter period of 2020–2021 in the Kyiv region. The used material was easily assembled premises of different types and sizes: easily assembled ones without insulation elements; with elements of warming and premises with deep-litter. In each of the studied premises were kept 400 dairy cows. The studies were performed during two periods: the first period had ambient temperatures from -10 to -14.9 °C and the second one from -15.0 °C and below. In our studies, the average daily temperature (during the ambient temperature from -10 to 14.9 °C) in easily assembled premises with the use of insulation elements was 6.20 and 5.31 °C higher than in premises without insulation and deep-litter. A similar trend was observed during the period of lowering the ambient temperature up to 15 °C and below. Thus, the advantage of the premises without insulation constituted 6.28 °C, and of the premises with deep-litter per 5.84 °C, respectively. It was found that keeping in easy-to-assemble premises with insulation elements, the consumption of free thermal energy from the whole herd during the experimental periods was lower compared to the keeping in a boxing cowshed and a cowshed with deep litter. This is due to the smaller range of fluctuations in the average daily temperature in a room with insulation elements. A similar trend was observed for energy consumption through enclosing structures and for moisture evaporation and, accordingly, total heat consumption. In general, heat deficiency was observed during the keeping of cows in the investigated premises of easily assembled type at negative temperatures (-10–14.9 and -15 °С and above). Accordingly, the thermal balance of the premises was negative. The highest values of heat balance among easily assembled premises in both research periods were observed for keeping in rooms that used insulation elements.

Field Study on the Thermal Performance of Vacuum Tube Solar Collectors in the Climate Conditions of Western Norway

A significant part of energy consumption in Northern countries goes to heating. There is no consensus about the most efficient source of renewable heat there. This paper presents a field study for a 7.8 m2 vacuum tube solar collector facility that is conservatively located in the cloudy and cold climate conditions of western Norway. We analyse a year-long operation by examining the rig’s statistics. We show that in Nordic latitudes with rainy climate conditions, a domestic solar hot water system can produce 2200 kWhth/y at a thermal efficiency of up to 72%. The average amount of heat produced by the collectors was up to 14.7 kWhth/d. This was enough to sustain the domestic hot water demand in an average Norwegian household for 6 months with a short period of auxiliary heating. In conclusion, we calculated that a 3× upscaled area facility would deliver over 25 kWhth covering six months of total heat consumption. The payback period for the facility is 12 years.

Feasibility of construction and installation site of differential pressure sensors for gas energy efficient plant for coarse and fine purification

The paper substantiates the construction and location of differential pressure sensors for a coarse and fine gas energy-saving plant. Energy saving is achieved by installing filtering cylindrical elements of fine and coarse purification one inside the other, optimizing their shape and substantiating the location of the differential pressure sensors. The results of the studies show that the total specific heat consumption for heating and ventilation of purification plants from all energy-saving measures for the proposed option is 1.85 times lower than the existing analogue of the non-optimized shape and measuring the pressure drop at the inlet and outlet branch pipes. The article also proved that the static gas pressure in the lower part of filter elements of the coarse and fine purification will always be higher than in their upper part. This results in a proportionally higher amount of inlet gas and therefore more solids settling in the bottom of the filter element. Measurement of the pressure drop in the lower part of the filter element, the most clogged with solid particles, makes it possible to receive a signal at the dispatching console earlier and provides a time reserve for technical personnel to timely remove accumulated blockages from coarse purification elements and prompt replacement of fine purification elements.

Temperature field and anti-freezing system for cold-region tunnels through rock with high geotemperatures

The tunnels of the Sichuan-Tibet railway reach altitudes of above 4200 m and have very deep burial depths; thus, serious freeze and heat damage will be encountered during the long-term usage of these tunnels. Taking the Zilashan Tunnel as an example, the dynamic change in the temperature field during tunnel operation was studied by using a transient heat transfer model that coupled convection and conduction. The results show that a high geotemperature fails to directly eliminate freeze damage of the tunnel entrance. The temperature of the tunnel section with a low original geotemperature changes periodically, and the train-induced wind dramatically affects the temperature field. After long-term operation, the surrounding rock a certain distance from the tunnel wall in the radial direction maintains the original high geotemperature, serving as a stable heat source. To prevent and control the freeze damage of tunnels and utilize the high geotemperatures, an efficient and energy-saving anti-freezing system was proposed using an air-source heat pump in a heat extraction tunnel. The calculation method of the anti-freezing system was proposed, and the effect of the length of the extraction tunnel on the air temperature and coefficient of performance (COP) was also studied. The total heat consumption required for freeze damage prevention was obtained. Considering the energy loss of the transmission system, the maximum heating load of Zilashan Tunnel’s heating system was determined to be 37.23 kW. In addition, it is suggested that the length of the extraction tunnel is 60 m, and the resulting COP of the air-source heat exchanger is 4.75. These research results can support anti-freezing design for cold-region tunnels through rock with high geotemperatures.

Field tests on the operational energy consumption of Chinese district heating systems and evaluation of typical associated problems

Worldwide, China has the largest district heating (DH) area and is also the fastest growing country. This paper presents field measurement results for operational energy consumption from 38 DHSs to fill in the gaps in understanding of the current operational issues of the district heating system (DHS). The average heat consumption during the heating period was 98.6 kWh/m2 and the monthly average electricity consumption for circulating pumps in the primary and secondary networks was 0.27 kWh/(m2 × month) and 0.29 kWh/(m2 × month), respectively. Thereafter, a systematic method for breaking down the energy consumption and quantitatively evaluating the underlying problems is presented. Based on several detailed measurements conducted in typical heat-exchange substations (HESs), it was found that overheating was the most prominent problem in energy-efficient buildings, constituting 23% of the total heat consumption. Another problem encountered was heat loss through pipes, which constituted approximately 5%–10% of the total heat consumption and was highly dependent on the actual conditions. In distribution networks, problems such as high resistance, high operational flow, and low pump efficiency were also identified and analyzed. Finally, practical energy-efficiency suggestions and future potential targets for the Chinese DHS are discussed from both a design and operational perspective.

A parametric simulation on the effect of the rejected brine temperature on the performance of multieffect distillation with thermal vapour compression desalination process and its environmental impacts

AbstractMultieffect distillation with thermal vapour compression (MED–TVC) is one of the most attractive thermal desalination technologies for the production of freshwater. Several mathematical models were presented in the open literature to analyse the steady‐state performance of such process. However, these models have several limitations and assumptions. Therefore, there remains the challenge of having a reliable model to accurately predict the performance of the MED process. Thus, this research attempts to resolve this challenge by rectifying the shortcomings of the models found in the literature and create a new one. The robustness of the developed model is evaluated against the actual data of Umm Al‐Nar commercial plant situated in UAE. In seawater desalinisation, a large amount of high‐salinity stream (brine) is rejected back into the sea. This paper investigates the influence of the rejected (exit) brine temperature on the system performance parameters of MED–TVC process. Specifically, these parameters are considered as total heat consumption, gain output ratio, freshwater production, heat transfer area and performance ratio. Also, the particular parameters of TVC section of the entrainment ratio, compression ratio and expansion ratio are also addressed. Moreover, a critical evaluation of the influence of the rejected brine temperature on the seawater is also embedded.

Performance Evaluation of Alternating Current Square Waveform Submerged Arc Welding as a Candidate for Fabrication of Thick Welds in 2.25Cr-1Mo Heat-Resistant Steel

AbstractThe paper evaluates the performance of alternating current (AC) square waveform submerged arc welding (SAW) as a candidate technology for manufacturing thick welds for high-pressure vessels. A new mathematical formulation for calculating melting efficiency in square waveform arc welding is presented. The melting efficiency and the heat consumption are presented as a mathematical model of welding parameters, namely welding current, welding speed, current frequency, and electrode negativity (EN) ratio. The proposed approach is demonstrated through the welding of 2.25Cr-1Mo heat-resistant steel performed over a wide range of welding parameters. The investigation provides deeper insights into the interplay between process parameter, total heat consumption, and melting efficiency. The effect on flux consumption is also explained. The melting efficiency is inversely proportional to flux consumption. The welding heat does not necessarily promote the plate melting. Improper use of welding heat may lead to decreased melting efficiency and increased unwanted melting and consumption of welding flux. Compared to the conventional direct current (DC) power sources, the AC square waveform welding achieves almost the same order of melting efficiency with added advantages of better weld bead shape and flux consumption in a desirable range. The two additional parameters (frequency and EN ratio) of the AC square waveform power source provide more freedom to fine-tune the process and thereby efficiently use welding heat. The results of this investigation will be advantageous to the designers and fabricators of high-pressure vessels using AC square waveform welding.