Heat Balance Research Articles

Primarily experimental study of the energy performances of a humidification-dehumidification seawater desalination system coupled with a heat pump

The study presented in this article explores a comprehensive analysis of a humidification-dehumidification (HDH) seawater desalination system integrating a heat pump for heating seawater intended for distillation, and incorporates additional condensation plates supplied with cold seawater. This system was the subject of an experimental investigation to simultaneously evaluate the energy performance of the heat pump and the thermal behavior of the desalination unit, focusing on seawater and condensation wall temperatures, as well as the stratification of temperatures of humid air inside the unit compared to the evaporation surface. Experimental results showed an average daily production of distilled water of approximately 32.75 kg/m² per day, with an electrical consumption of 37.68 kWh/day, which was reduced to 26.72 kWh/day through the integration of photovoltaic solar energy. Based on heat and mass balance equations of all the system’s components, the study used a detailed thermodynamic model. The system's energy performance was analyzed by calculating the coefficient of performance (COP), the specific energy consumption (SEEC), and the gain output ratio (GOR), reflecting the overall energy efficiency of the HDH system coupled with the heat pump, as well as the recovery ratio (RR), indicating the proportion of the recovered water compared to the input water.

Recycling of lead from spent batteries in the Trepça complex in Mitrovica,Kosovo

In this paper, research has been done on the possibilities of recycling lead from secondary materials, with special emphasis from spent batteries and that through pyrometallurgical processes. The recycling of lead from spent batteries is different in different countries, for example. in America it is 85%, while in Germany, France, Italy it is about 90%, and Japan with 95%, but there are also companies that base their production mainly from secondary lead materials and from spent batteries, pipes, plates, rods, etc. Such a process is designed for the recycling of spent batteries in the former Mining and Metallurgical Combine "Trepça" in Mitrovica, where the production rate was about 15,000t/y, but the max. capacity. of production was up to 20,000 t/y spent batteries. The battery plant is in good condition, but the rotary furnace and connected off-gas treatment systems are not operating and the old refinery is in a poorer condition, so the design is done for all operations in the new refinery. Mass and heat balance was also done. For the purpose of defining the demands of the unit for the bag filter, in the rotary furnace. The work is reasonable not only from the economic aspect of the exploitation of useful metals, but also from the environmental aspect, due to the fact that the toxicity of such a material is even wider.

Three approaches to modelling heating and evaporation of monocomponent droplets

Three approaches to modelling the heating and evaporation of monocomponent droplets are compared. Firstly, the heat rate supplied to the droplets to raise their internal energy is calculated based on the observation that steady-state equations for heat and mass balance in the gas phase should lead to the same droplet evaporation rates. The direct calculation of the above-mentioned heat rate is used in the second approach; the value of this rate is then used for the estimation of the droplet evaporation rate using the Spalding heat transfer number. In the third approach, the same algorithm as in the second approach is used to calculate the heat rate but the mass evaporation rate in this approach is inferred from the coupled solution to the momentum, mass and energy conservation equations in the gas phase; the gas mixture density in this approach depends on temperature. The predictions of the numerical algorithms for these approaches are compared with experimentally observed time dependencies of the rates of change of radii and average temperatures of n-decane droplets at initial temperatures and radii equal to 300 K and 0.85 mm, respectively, placed in a gas at temperatures 500 K and 760 K. It is shown that the algorithm for the third approach predicts values which are close to the experimental data.

Effective ignition energy for capacitor short-circuit discharge in explosive environments

Capacitors short-circuit discharge in an explosive environment can ignite and detonate the surrounding explosive media, causing dangerous accidents. At low voltages, this kind of discharge constitutes a micro-nano discharge; because the discharge gaps here are of the order of only microns to nanometers, the discharge process, electrode energy consumption, explosive media ignition energy, and other energy relationships are unclear. To study the relationships between the capacitor storage energy and various kinds of dissipation energies under short-circuit discharge, a model comprising conical and spherical cylinder microbumps is proposed based on the cathode surface morphology obtained by three-dimensional profiling and scanning electron microscopy, respectively. Then, the second-order non-chi-squared differential equations were established based on the principle of energy conservation and heat balance to deduce the relationships between the cathode surface temperature and height of the microbump, conical angle, and spherical radius; further, the energy consumed by the anode surface is calculated based on the theory of heat transfer. Using heat conduction theory, the energy consumed by the microbumps on the cathode surface is calculated, and the energy consumed on the anode surface is deduced using the surface heat source as the loading heat source. The residual energy of the capacitor is calculated from the discharge time and voltages before and after discharge, and the effective energy of the gas is calculated using the law of conservation of energy. Finally, the discharge channel energy, electrode energy consumption, and end residual energy of the discharge capacitor are used to derive the effective ignition energy of the explosive gas. This research is of great significance for the design of intrinsically safe circuits with high power.

Evaluating long-term operational data of a Very Large Crude Carrier: Assessing the diesel engines waste heat potential for integrating ORC systems

Given the spotlight on waste heat recovery (WHR) technologies for decarbonizing the shipping industry, critically assessing waste heat from propulsion and auxiliary engines using actual data is crucial for accurately predicting fuel and carbon savings. This paper addresses this by applying advanced data processing, considering voyage characteristics, and developing methods for mapping waste heat from main engine (ME) and diesel gensets (DGs) operations using long-term operational data from a Very Large Crude Carrier (VLCC) case study. Two methods predict unrecorded air mass flows by implementing heat balance: one using measured temperature values and the other estimating exhaust gas mass flow rates based on fuel oil consumption. Within the main objectives of this study is to examine the impacts of employing the exhaust gases of both ME and DGs to evaporate recuperative ORC working fluid on power output and vessel annual carbon savings, with the formed diesel engines operational profiles serving as inputs. Simulations show a power output of 530 kW using ME exhaust gases, increasing to 653 kW and 741 kW with DGs integration for R245fa and R1233zd(E) as the selected ORC working fluids, respectively. The proposed solutions can reduce annual CO2 emissions by 4 % to 7 %.

Microstructural and kinetics analysis of FeB–Fe2B layer grown by pulsed-DC powder-pack boriding on AISI 316 L steel

In this study, novel findings were obtained regarding the influence of a 10 A current intensity on the growth of an FeB–Fe2B layer during pulsed-DC powder-pack boriding. Boride layer formation was carried out on AISI 316 L steel at 1123–1223 K for different exposure times at each temperature, considering 10 s polarity inversion cycles. The boride layer was characterized by x-ray diffraction and high-speed Berkovich nanoindentation, the latter being used to determine the hardness and reduced Young’s modulus mappings along the depth of the layer-substrate system. Moreover, the growth kinetics of the FeB–Fe2B layer on the steel’s surface was modeled using the heat balance integral method (HBIM). This involved transforming Fick’s second law into ordinary differential equations over time, assuming a quadratic boron concentration profile in space to determine the B diffusion coefficients in FeB and Fe2B, respectively. From the Arrhenius relationship, the B activation energies in the boride layer were estimated considering the contribution of the electromigration effect; the results showed an approximately 30% reduction compared to the values obtained in the conventional powder-pack boriding for AISI 316 L steel. Finally, the theoretical layer thickness obtained by the HBIM demonstrated an error of no more than 5% against the experimental FeB and FeB + Fe2B layer thickness values.

Continuous composite longitudinal fins under oscillating boundary conditions: a lattice Boltzmann solution

PurposeTransient response of continuous composite material (CCM) fin made of high thermally conductive composite material is presented. The continuously varying effective properties of composite material such as thermal conductivity, heat capacity and density have been modelled using the Mori-Tanaka homogenization theory and rule of mixture. Additionally, temperature dependency of thermal conductivity, heat generation (composite materials) and convection coefficient (fluid properties) have also been incorporated. Different base boundary conditions are addressed such as oscillating heat flow, oscillating temperature, step-changing heat flow and step-changing temperature. At the other boundary, the fin is assumed to have a convective tip.Design/methodology/approachLattice Boltzmann method is implemented using an in-house source code for obtaining the numerical solution of typical non-linear heat balance equation of the aforementioned problem under various transient base boundary conditions.FindingsThe effects of various thermal parameters such as material diffusivity ratio and conductivity ratio, area ratio and Biot number on transient response of fin and temperature distribution of fins are studied and interpreted. The heat transfer rate and time for attainment of steady state temperature of metal matrix composite (MMC) fin are found to be proportionally dependent on their diffusivity ratio. Additionally for higher values of area ratio and biot number, MMC fins are reported to dissipate the heat more efficiently in comparision to homogeneous fins in terms of time required to attain the steady state and surface temperature.Practical implicationsResponse of transient fin associated with advanced class of material can facilitates the practicing engineers for designing high-performance and/or miniaturized thermal management devices as used in electronic packaging industries.Originality/valueStudies of composite fin consisting of laminating second layer of material over the first layer have been reported previously, however transient response of CCM fin fabricated by continuously varying the volume fraction of two materials along the fin length has not been reported till date. Such material finds its application in thermal management and electronic packaging industries. Results are plotted in form of a graph for different application-wise material combinations that have not been reported earlier, and it can be treated as design data.

Glass capillary array supported membrane evaporator balancing heat and water management for double-side solar-driven interfacial evaporation

Efficient heat and water management are two important aspects for boosting solar-driven interfacial evaporation. Here, we develop a glass capillary array supported membrane evaporator (GCSE) to simultaneously achieve heat and water management. In the GCSE, a membrane at top regions enables photothermal conversion, and a glass capillary array at bottom regions serves as both water and heat management. The balance of heat and water management can be readily controlled by adjusting the number and height of glass capillary array. Moreover, the exposed bottom surface of GCSE further utilizes extra evaporation surface to boost evaporation. As a result, a high evaporation rate of 2.06 kg m−2 h−1 with an efficiency of 98.6% under 1 sun is achieved. Furthermore, the GCSE also exhibits potential applications in oil/water emulsion purification and seawater desalination.

HEAT BUDGET OF THE BARENTS SEA SURFACE IN WINTER

Variability of the total heat balance (HB) of the Barents Sea during the cold period of the year has been studied. The cold period is that of cooling of the sea surface when the heat flux is permanently oriented towards the atmosphere. The contribution of two major components of the HB, i. e. sensible and latent heat fluxes, to the observed increase of the total winter heat transfer at the sea-atmosphere interface has been estimated. Data on short-wave and long-wave radiation fluxes, and sensible and latent heat values were obtained from the atmos-pheric reanalysis of the European Center for Medium-term Weather Forecasting ERA5. HB of the sea surface was calculated as a sum of short-wave and long-wave radiation fluxes and those of sensible and latent heat. The total HB, as well as the total flux of sensible and latent heat for the cold period were calculated by summing up the corresponding values between the start and end dates of the cooling season. Calculations demonstrated an increase in the sum of HB over the cold season for the northern part of the Barents Sea (up to 2000 MJ/m2 over 40 years), and a decrease in the southern part of the sea (up to 1000 MJ/m2 over 40 years). In the northern part of the sea, the contribution of sensible and latent heat fluxes decreases to 0,3-0,4. The observed trend of sum of HB over the cold season and its turbulent components could with high probability be explained by increasing difference between air temperature and sea surface temperature.

Micro-scale fuel cell cogeneration system response combined with heat pump consumption in arid zones

This study aims to evaluate a new concept for Cogeneration Energy System (CES) designed to supply an area of 80 m2 located in an arid zone (Southern Algeria). A heat balance is conducted on a prototype house using real data. Numerical simulations are performed to test the heat balance with a Proton Exchange Membrane Fuel Cell PEMFC sub-system (PEMFCs). The design targets to provide both electrical and thermal energy required for the house. Simulation and energy balance allow to assess the heat transfer of the entire system for both heating and cooling operation modes. The variations in critical temperatures at the inlets and outlets of the heat storage tank, the energy transferred from the PEMFCs to the load, and the required hydrogen quantity are determined. In heating mode, the cogeneration efficiency of the PEMFCs stands at around 68.5 %, while the CES efficiency ranges between 65.8 % and 67.3 %. In cooling mode, the PEMFCs efficiency ranges from 64.5 % to 68.5 %, with CES efficiency also ranging from 64.2 to 66.2 %. Based on these findings, the CES for a home in an arid region requires a maximum power of approximately 1 kW and a hydrogen consumption of 5 kgH2.

Heat Balance Method of Computing the Cooling Modes of Large-Sized Optics in Vacuum

Heat Balance Method of Computing the Cooling Modes of Large-Sized Optics in Vacuum

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.

НОРМИРОВАНИЕ ВОДОПОТРЕБЛЕНИЯ СЕЛЬСКОХОЗЯЙСТВЕННЫХ УГОДИЙ И КУЛЬТУР С УЧЕТОМ ПРОСТРАНСТВЕННО-ВРЕМЕННОЙ ИЗМЕНЧИВОСТИ ГИДРОМЕТЕОРОЛОГИЧЕСКИХ ФАКТОРОВ

The article presents the developed calculation methodology for environmental regulation of water consumption of agricultural land and crops, taking into account the spatiotemporal variability of climatic, hydrological, soil and biological indicators of the natural system. It is noted that the human pressure in the form of a deficit in water consumption of agricultural land and crops should be based on the principles of energy balance of heat, moisture and nutrients, taking into account natural conditions that ensure targeted regulation and management of soil-forming processes in hydro-agrolandscapes. The developed model and algorithm for assessing water consumption in agriculture are built using two models for rationing water consumption - agricultural land and crops, which makes it possible to determine the most important criteria for environmental management in irrigated agriculture and is of great importance in ensuring food security of the population.

Experimental investigation on the preparation of macroscopic 0–1 mm powdered coal by a vertical spindle mill

The vertical spindle mill (VSM) is the key equipment to realize the preparation of 0–1 mm fuel used in powdered-coal-fired circulating fluidized bed combustion technology (PC-CFB). In this paper, a pilot-scale VSM test system was set up to explore the feasibility and operating performance of coarse-grained pulverized coal preparation. The effects of loading force, table revolution rate, and ventilation rate on the product size distribution, as well as the energy consumption of the grinding process were emphatically discussed. The results show that the product size of VSM increases with the decrease of loading force and the increase of ventilation rate, but too small a loading force will affect the normal output of VSM. Additionally, the product size of VSM decreases firstly and then increases with the increase of table revolution rate. Further, the energy consumption of the powdered coal preparation process was quantitatively described, and a semi-empirical model of comminution energy based on the powdered coal particle size distribution was proposed and verified by the measured values with an average accuracy of ±30 %. This model can estimate the power consumption of the mill, which can be used as an input parameter of the heat balance calculation model for the PC-CFB pulverizing system.

Improving Quality Control Measures in the Dairy Industry: Utilizing Dynamics of Dirt Resistance Factor (Rd) Value and Time of Effective Bacterial Contamination Prevention

The number of customer complaints related to decreased quality of dairy products was the background of this study. Objective: (i) examined the effect of the highest dirt resistance factor (Rd) on the number of bacterial contaminants in finished goods; (ii) examine the effect of time on the growth of bacterial contaminants in the fouling layer of UHT pipes when not in operation. The research method was based on the mathematical derivation of the formation process of Rd in the form of an equation. Bacterial species were analyzed using the Operation Taxonomic Unit (OTU) with 16S rRNA. The ANOVA test was used to determine the mean value, standard deviation and the Tukey LSD post hoc test to see the difference in heat balance and bacterial growth. Findings: (i) During the UHT sterilization process, the Rd value (0.0205 h.Ft2.F.Btu-1) had an impact on total bacterial contamination >20 Cfu.mL-1; (ii) In the event of engine damage or malfunction of the heater on the UHT. Time had a significant effect (p<0.05) on the number of lactic acid bacteria in the fouling layer in UHT pipes. Conclusion: The study recommends a sanitation schedule every 110 minutes (± 2 hours) or Rd value around 0.0205 h.Ft2.F.Btu-1.

Wpływ zmian klimatu na środowisko zabudowane

We are currently in the period of an intensive climate change, resulting from changes in the heat balance of the earth’s surface and causing an increase in the temperature of the lower troposphere levels. According to the latest IPCC report of 2021, it is human activity that has indisputably caused the increase in atmospheric concentrations of greenhouse gases, responsible for this process. The consequences of climate change under Polish conditions, apart from a rise in temperature especially in the spring and winter months, are also changes in the amount and distribution of precipitation totals. A slight increase in precipitation totals is observed, however heavy rainfall is significantly more frequent, interspersed with periods of droughts and heatwaves. Ground frost-free periods are prolonged, and a negative trend in the duration and thickness of snow cover is recorded in most parts of the country. Although extreme phenomena occurring in Poland are permanently inscribed in its climatic conditions, the threat of strong winds has been increasing in recent years, and the intense precipitation that often accompanies them is the cause of peak discharges and flooding. Forecasts for progressive climate change are not optimistic, either on a global scale or for the country in question. The article examines the impact of climate change on the design, construction and maintenance of engineering structures globally and for Poland. Changes in design standards, selected examples of disasters and solutions to adapt and build resilience to climate change have been analysed. For most building disasters, climatic factors were the direct cause of the disaster, although in the course of the analysis it has usually turned out that the disasters exposed human errors in the design, construction and, to a lesser extent, the improper maintenance of engineering structures. However, there is an increasing number of new approaches to creating a climate change resilient built environment, including the latest one, which proposes to use the grey infrastructure of cities to build resilience to climate change.

Condensation characteristics of flows in newly developed three-dimensional enhanced heat transfer tubes

Condensation heat transfer characteristics were studied experimentally in order to evaluate the heat transfer performance of horizontal copper heat transfer tubes (smooth and enhanced). Using R410A and R32 as refrigerants, condensation heat transfer experiments were carried out for a saturation temperature of 45 °C; inlet vapor quality of the tube was 0.8 and outlet quality was 0.2; refrigerant mass flow rate range was in the range from 68 to 371 kg/(m2·s). Single-phase heat balance verification found that the heat loss is less than 6 %, with the deviation between single-phase experimental results and various correlations being less than 15 %. The condensation heat transfer coefficient increases with an increase in mass flow; as the mass flow rate increases, the turbulence of the liquid flow increases and the liquid film becomes thinner; thermal resistance is reduced and the heat transfer coefficient (HTC) increases. Experimental results determined that the performance factor ratio (enhanced tube/smooth tube) of the three-dimensional surfaces investigated here are greater than 1. Tubeside heat transfer enhancement factor (EF) of the HB/D tube is the highest (max 1.76); its performance is closely related to increasing fluid turbulence and improving drainage. Performance factor (PF) of the HB/D tube (max 1.38) is the highest for most of the flowrates. All this indicates excellent thermal performance. Flow model-based analysis was performed in order to develop a correlation for the condensation heat transfer coefficient and the pressure drop for the enhanced surface tubes. Both prediction models accurately predicted all data points within a limited margin of error.

Investigating the transient conditions of “Sabat” space and its influence on pedestrian sensations during thermal walks. Algiers’ Casbah case study

Cities are already witnessing the impacts of climate change. Prolonged heat exposure have a direct effect on pedestrians’ thermoregulatory system, causing serious heat-related issues in the form of fatigue and thermal exhaustion. While the human body is capable of maintaining heat balance, excessive heat exposure combined with increasing heat loads can deteriorate the thermoregulatory process which leads to discomfort. Walkability is one of the significant challenges for climate change mitigation. Balancing the dichotomy of walking to mitigate climate change, and mitigating climate change to walk emphasizes the importance of promoting resilient walkability. In this context, the term “resilience” is used to highlight the need to design urban spaces able to adapt to increased urban heat, enabling pedestrians to tolerate and recover from discomfort conditions. This study investigates the potential of the “Sabat”, a traditional semi-outdoor space with lift-up design, and its distribution in generating transient thermal aeraulic conditions, and reducing fatigue sensation, hence, supporting a positive walking experience. Thermal walks have been conducted in Casbah of Algiers during temperate and hot weather conditions, in the context of uphill walking. Results revealed the alliesthesial effect of cool-shaded and ventilated Sabats to reduce fatigue sensation, which was confirmed by the significant correlation at lag-(-1) (r = 0.504, p < 0.001). Findings shed light on the importance of maintaining dynamic alliesthesia to create modulated restorative opportunities and offer starting point for hypothesizing broader trends for future implementation of Sabat design in modern cities.

Thermal Efficiency in Steel Reheating Process

In this study, the energy consumption by theprocess of steel billet reheating in an industrial steel reheatfurnace at the Libya Iron and Steel Company (LISCO) isconsidered. It is known that in the steel industry, one of the processes requiring the most energy is the process ofreheating the steel prior to hot rolling. A comprehensivemass and heat balance was performed on the furnace, takinginto account all actual entering and exiting furnaceparameters. Furnace thermal efficiency was found to be lowand heat losses from different areas of the furnace wereconsiderable.

Estimating the income-related inequality aversion to energy limiting behavior in the United States

Distributive energy justice is measured by the degree to which, and whether, different members of society have equal share in the benefits and burdens of the energy system. One way to achieve distributional energy justice is to ensure all households, regardless of income, can use as much energy as they need to heat and cool their home to desired temperature. We define a household's cooling balance point (CBP) as the ideal set temperature at which the household desires to keep its living space in summer; the heating balance point (HBP) is defined as the ideal set temperature in winter. To quantify the extent to which balance points were disproportionately concentrated among certain income groups, we used the extended concentration index. This index has an inequality aversion parameter that reflects the value judgment of a society. If this parameter <1, the society is pro-rich; if this parameter >1, as it increases, the society becomes more pro-poor. We estimated the empirical value of the income-related inequality aversion in eight U.S. states and examined several effects of demographic characteristics on inequality aversion.In an online survey, 1066 (from four southern states) and 906 (from four Midwest states) participants made choices between energy policies leading to different distributions of CBP (southern) or HBP (Midwest) across five income groups in a hypothetical society. Participants showed a pro-poor propensity: the median inequality aversions were 1.37, 95% CI of [1.35, 1.39] (CBP) and 1.56, 95% CI of [1.56, 1.60] (HBP). For both CBP and HBP: younger participants were less averse to inequality. For CBP, blacks (vs. whites) and conservatives (vs. centrist) were less averse to inequality; for HBP, Hispanics (vs. whites), low (vs. high) education participants, and those whose homes were well insulated (vs. adequately and vs. poorly insulated) were less averse to inequality. Our findings provide insights into how the broader public values energy justice, which further provides important policymaking implications.