Water Heating Research Articles

Heat-confinement, water-resistance, and moisture-release electrospun membrane based on aerogel filler incorporation

The maintenance of a comparatively stable human body temperature through heating is essential for numerous physiological activities. However, the majority of the existing heating strategies are inefficient and wasteful in terms of energy usage, while also falling short in sufficiently protecting the human body against environmental hazards. Fabrics possessed the abilities to retain heat, repel water, and permit moisture to travel through are in high demand, which are essential for energy conservation and protective purposes. Herein, we introduce a highly efficient approach for producing electrospun membranes that exhibit excellent properties of heat confinement, water repellency, and moisture release properties, achieved by incorporating SiO2 aerogel fillers into interconnected nanofibers. As a result, the obtained aerogel filler incorporation membrane (AFIM) composed of PVDF@SiO2 exhibited a reduced thermal conductivity and reinforced moisture-release capability, leading to a 2 °C increase in temperature differential over its cotton counterpart and a water vapor transmission rate (WVTR) of 26.83 kg•m−2day−1. This work offers insights into the advancement of the thermoregulatory textiles to conserve energy and prevent waterlogging in future challenging conditions.

Physiological and behavioral indicators of water buffaloes with access to heat mitigation resources in a grazing system during the hot season in the subtropics

Water buffaloes are increasingly being raised in similar way to dairy cows, in grazing systems frequently deprived of shade and water for immersion. This study aimed to evaluate the effects of different heat mitigation resources, 1) only shade and 2) shade plus water for immersion, on the behavioral repertoire and physiological characteristics of female grazing buffaloes in the subtropics during the hot season. Twenty buffaloes (Bubalus bubalis), including calves, heifers and non-lactating cows were allocated throughout the hot season (from December 2021 to April 2022) in a grazing system with two different heat mitigation resources (treatments): only shade (SH) and shade plus water for immersion (SHW). Diurnal behavioral repertoire was recorded every 15 days, individually and focally, at every 5 minutes for 12 hours per day. Heart rate (HR; beats/min), respiration rate (RR; breaths/min), rectal temperature (RT; °C) and panting score were also measured. Buffaloes reduced grazing time especially with THI above 75. Buffaloes at SHW spent more time grazing and lying than SH buffaloes (P < 0.05). Cows and heifers had higher ruminating (P < 0.05) and standing time (P < 0.05) compared with calves. Physiological variables did not differ (P > 0.05) between treatments (SH vs. SHW) and were positively correlated with air temperature and THI (P < 0.05). HR was higher for heifers (59.6) and calves (63.5) than for cows (53.3; P < 0.05). RT tended to be higher for heifers (38.4) and calves (38.3) than for cows (38.1; 0.05 < P < 0.10). However, respiration rate did not differ across buffalo categories (P > 0.05). Panting behavior was not reported throughout the observation days (panting score = 0). When both heat mitigation resources, shade and water for immersion were available, buffaloes preferred water for immersion to mitigate the effects of heat stress. Regardless animal category, buffaloes were able to maintain physiological variables within the normal range, indicating that providing shade and/or water for immersion, as environmental enrichment resources for thermoregulation, is suitable for heat stress mitigation in water buffaloes throughout the hot season in the subtropics.

Optimizing energy efficiency in mediterranean single-family homes: A parametric study of building typology, orientation, and BIPV integration

The energy efficiency of residential buildings is a critical concern, especially in regions with challenging climatic conditions like the Mediterranean. Despite numerous studies on energy-efficient design, there is a lack of specificity in how building typology, orientation, and Building-Integrated Photovoltaics (BIPVs) interact to influence energy performance. This study addresses this gap by conducting a parametric investigation of single-family houses, focusing on variations in building typology and orientation, both with and without BIPV integration. The parameters evaluated include energy consumption for heating, cooling, lighting, and domestic hot water, using simulations performed with iSBEM-Cy, the official tool for energy performance calculations in Cyprus. The results reveal that building orientation can reduce energy consumption, while BIPV integration contributes additional energy savings. Terraced houses with only Building-Applied Photovoltaics (BAPVs) showed the best energy balance (−38.20 kWh/m2/yr), while detached houses had the highest energy consumption (71.24 kWh/m2/yr). With BIPVs, energy balances improved significantly across all typologies, with terraced houses reaching −78.20 kWh/m2/yr, demonstrating the strong potential of BIPV integration. These findings highlight the importance of considering context-specific factors when integrating renewable energy systems, offering insights for architects and urban planners.

Efficiency-aware machine-learning driven design of solar harvester for renewable energy application

Although MIM structures have been studied for solar thermal applications for decades, the multilayer MI-MIM structure is the subject of this study's investigation for batter absorption. In order to identify an effective solar absorber, two configurations Gold-MgF2-Gold (GMGSA) and Gold-MgF2-Gold-MgF2-Gold (GMGMGSA) are examined in this work. By using machine learning approaches, this research was able to get an MSE of 2.8091 × 10−5 and an R2 value of 0.998836. The optical response and parameter optimization analysis have been examined in this work in the wavelength range of 0.4 μm–1.6 μm. When exposed to AM 1.5 spectrum radiation, the GMGMGSA absorbs 93.10 % of the radiation, compared to 88.30 % for the single-layer GMGSA. Furthermore, both structures show steady absorption that is independent of polarization up to a 70° incidence angle. The aforementioned discoveries render the structure a plausible contender for solar thermal uses, including battery-integrated photovoltaic (BIPV), commercial solar power (CSP), and solar water heating. This might lead to a future where energy is more sustainably produced.

IoT-based real-time biofloc monitoring and controlling system

In Bangladesh, Biofloc technology is becoming popular in aquaculture, but controlling water parameters effectively remains a key challenge for achieving high yields. In this study, a system was proposed that continuously analyzes biofloc regulating parameters, such as temperature, total dissolved solids (TDS), potential of hydrogen (pH), turbidity, dissolved oxygen (DO), and water level, to maintain the ideal circumstances for biofloc. An Internet of Things (IoT)-enabled platform was implemented to collect and analyze real-time data from sensors, including the DS18B20 water temperature, pH-4502C, analog dissolved oxygen, analog total dissolved solids, and water level sensors. The experiment was conducted with mono-sex Nile tilapia (Oreochromis niloticus). The ESP32 microcontroller utilized Wi-Fi to process sensor data, enabling real-time data analysis on mobile and computer devices through the Blynk application. The study was done as per designated conditions, and that led to the average value of temperature around 27±1 °C, DO around 6 ± 0.5 mg/l, TDS around 500 ppm, and the pH level was nearly 7.7 ± 0.5. If the temperature, water level, or dissolved oxygen changed from the expected value, it sent a signal to the Blynk. This signal then autonomously operated a relay to activate or deactivate the water heater, pump, and air pump to maintain an effective operating condition. Hence, IoT-enabled monitoring systems can have a crucial impact on managing the biofloc throughout the year and enhancing the aquaculture industry in Bangladesh.

Study the effect of adding rectangular fins along the riser pipe on the thermal performance of the flat‐plate solar water heater system

Study the effect of adding rectangular fins along the riser pipe on the thermal performance of the flat‐plate solar water heater system

Design and experimental characterization of a propane-based reversible dual source/sink heat pump

The current paper presents the design and energy performance analysis of a propane-based reversible Dual Source/Sink Heat Pump (DSHP). DSHPs offer an alternative to conventional water to water and air to water heat pumps, leveraging the strengths of both technologies in an efficient manner. The developed prototype incorporates an innovative Dual Source/Sink Heat eXchanger (DSHX), enabling the unit operating in various modes, including space heating, space cooling, and domestic hot water production using brine, air or both simultaneously as a source/sink. The DSHX serves as as both a condenser or an evaporator, directly rejecting or absorbing heat from air and/or brine. By eliminating secondary loops and defrost cycles, the DSHX minimizes energy losses. The main novelty of this work lies in the DSHX that integrates external units typically duplicated in DSHPs into a single component, eliminating the need for split refrigerant flow rates, thus avoiding maldistribution, refrigerant charge increase and draining valves. A steady state experimental campaign was conducted in a climatic chamber to characterize the DSHP prototype and validate the DSHX performance models. Heating capacity up to 11.2 kW and COP values up to 4.7 were achieved at nominal compressor speed by supplying hot water at 35 °C with an ambient temperature of 7 °C. Similarly, when producing cold water at 7 °C, cooling capacity and EER reached 9.8 kW and 3.6, respectively, at nominal compressor speed using air as heat sink at 35 °C. The effects of various operating parameters on the overall coefficient of performance and heat duty in both heating and cooling modes, considering air or brine as heat source/sink are analyzed in detail. Results demonstrate enhancements of approximately 15 % in capacity and efficiency compared to earlier work. Moreover, four deterministic models were created in order to predict the behaviour of the DSHX and validated against experimental results, reaching deviation values below 15 %.

Mathematical Study of a Double-Slope Passive Solar Distiller with Water Heater Condenser

In this article, the inevitable condensation losses from the back-side glass cover of a passive single-basin double-slope distiller (PSDD) were recovered in heating water inside a glass solar water heater (SWH) to produce hot water as an auxiliary product of the distiller. The transient thermal performance of the PSDD-SWH was mathematically modeled and compared to a conventional PSDD in actual weather circumstances. Compared to a conventional PSDD, the results revealed that the thermal efficiency of the PSDD-SWH increased by 18% to 83% during the day. In addition, increasing the water mass inside the water heater from 3kg to 18kg increased the thermal efficiency of the PSDD-SWH by about 50% despite decreasing the total distillate by less than 1%. Moreover, the thermal performance of the PSDD-SWH, in terms of distillate production, hot water temperature, and thermal efficiency boomed in hot climates with high solar irradiation and high ambient temperatures. Furthermore, insulating the glass covers of the PSDD-SWH during off-sun hours significantly enhanced the thermal performance of the PSDD-SWH.

Life cycle assessment of the manothermosonication of liquid whole egg: a comparative evaluation with conventional thermal preservation

Manothermosonication (MTS) is a promising alternative to thermal preservation of liquid whole egg (LWE) in terms of safety level and improved quality. However, energy and sustainability assessment of MTS are not well described. This study compared the energy balance and life cycle assessment (LCA) of MTS to traditional thermal preservation of LWE, considering equivalent microbial inactivation levels and a production capacity of 100 kg/h within a "gate to gate" approach.Results of the energy assessment indicated that MTS preservation consumed 15% less energy (2.00 kWh/kg of LWE) and water compared to thermal preservation (2.36 kWh/kg of LWE). This reduction is attributable to cavitation, the mechanism of action in MTS, which eliminates the need of pre-homogenisation stage and water for heating. Concerning the environmental impact, MTS scored lower in all impact indicators, mainly due to reduced electricity and water usage. For instance, carbon footprint of CO2 emissions from LWE processing were 57.3% for MTS and 61.8% for thermal preservation, with the environmental impact of the pasteurisation stage being 4.1-fold lower in MTS. This study suggests MTS preservation of LWE is a viable alternative to thermal methods, offering safety, quality, and improved energy and environmental benefits.

Coordinated price-based control of modulating heat pumps for practical demand response and peak shaving in building clusters

With a high share of renewable energy in the power grid, it becomes increasingly difficult to ensure a continuous balance between power generation and consumption, thereby endangering grid stability. A substantial opportunity to address this challenge and align the heating demand with intermittent power production is offered by space heating and domestic hot water, which account for 80% of the energy consumption in buildings. Further research on the control of building clusters is required, where peak load management of multiple buildings can ensure grid stability during peak hours and contribute to avoiding power outages. In this paper, a rule-based controller is presented, called Extended Price Storage Control+ (EPSC+), for the practical and flexible operation of heating systems in a building cluster. Under dynamic pricing, the loads of electric heating devices for the provision of space heating and domestic hot water are shifted by EPSC+ while accounting for peak load constraints. The performance of EPSC+ is evaluated in a nine-week winter simulation study with a building cluster of ten buildings in Germany. For comparison, a hierarchical model predictive controller (MPC) and a hysteresis two-point controller are employed as benchmarks. Results close to those of MPC are achieved by EPSC+by reducing the median peak load by 38.8% and median electricity costs by 15% compared with the hysteresis controller. In contrast to MPC, EPSC+ does not require models, forecasts, or optimization and is computationally inexpensive, rendering it more attainable for real-world implementation.

Water heater storage heat pump cycle for higher operating range

Heat pumps for water heating have become increasingly attractive. However, the achievable water temperature using a vapor compression heat pump water heater (HPWH) is often constrained by the compressor operating envelope. To address this challenge, HPWHs typically employ two-stage compression with complex system architecture or rely on back-up electric heating. This work introduces an alternate storage heat pump concept to improve the operating temperature range of an R134a HPWH system. The developed system operates in two modes: Mode I functions as a typical wrap-around condenser HPWH, while Mode II splits the wrap-around coil to use the top portion as a condenser and the bottom portion as evaporator. System modeling consisting of a vapor compression cycle and water tank sub-models was conducted to study the performance. The model was validated experimentally. The storage heat pump system could achieve an additional increase of 12 °C beyond the maximum possible water temperature of 46 °C which was achieved using the baseline conventional HPWH system. In Mode II, the system exhibits a 20 % higher average heating capacity and a 15 % lower average pressure ratio compared to the conventional system operating at a 27 °C ambient temperature. Compared to usage of electric heating elements, our system showed a longer recovery time with a 50 % lower energy consumption for a similar increase in water temperature.

Multi-criteria optimization next to a comparative analysis of a polygeneration layout based on a double-stage gas turbine cycle fueled by biomass and hydrogen

The significance and advantages of utilizing renewable energy sources are widely recognized. Upon examining past studies, it was revealed that there has been a lack of research on harnessing the waste energy from double-stage gas turbines powered by biomass-hydrogen hybrid fuel for polygeneration applications. Thus, a new configuration is proposed in the study for the multi-production of electricity, cooling, heating, and potable water. In the current research, a high-pressure turbine is driven by a combustion chamber fed by a biomass gasifier. Meanwhile, a low-pressure turbine is driven by a post-combustion chamber fed by hydrogen as fuel. The heat loss of the topping gas turbine cycle is recuperated by a supercritical Brayton cycle (SBC), a steam Rankine cycle (SRC), and a water heater. The waste heat of the supercritical Brayton cycle and steam Rankine cycle is recovered through an absorption refrigeration cycle and a thermoelectric generator, respectively. Thus, the heat loss of the topping system is completely recovered. The net power output of the gas turbine cycle is considered the electricity production of the system while the output power of the SBC and SRC is utilized in a reverse osmosis desalination system to produce potable water. The investigations conducted on the system are thermodynamic and exergy-economic assessments and three-objective optimization utilizing 5 gases (i.e., CO2, CO, Nitrogen, Air, and Helium) in the SBC. The final results reveal the superiority of Helium as the supercritical gas, bringing about an exergy efficiency () of 32.11%, a total cost rate () of 103 , a payback period (PP) of 0.159 years, and a specific cost of polygeneration () of 22.03 for the system. Although the levelized cost of products of the configuration is high due to the freshwater production, of the proposed system is higher than the previous systems based on a double-stage gas turbine cycle driven by biomass and hydrogen.

Numerical study of temperature distribution in a solar receiver with a focus on water heating in an internal helical tube

Solar energy is one of the clean energies that many researchers have focused on. This study used the Monte Carlo Ray Tracing (MCRT) method in MATLAB coding to calculate the water temperature inside a solar receiver containing a spiral coil through which water passes. To guess the amount of solar radiation that would hit the receiver and figure out the temperature of the water coming out, the Monte Carlo method was used. The three cases were: a change in the receiver's exposure time to solar radiation (t = 2, 4, 6, 8, 10 h); a change in the gas flow rate (Qg = 5, 10, 15, and 20 L/min); and a change in the water flow rate (from 2 to 20 with an increase of 2 L/min in each case. The study found that the gas volume flow rate (Qg) slightly affected the thermal distribution at Qg = 5 L/min, Tg = 358 C, and at Qg = 20 L/min, Tg = 352 C, while the water volume flow rate (Qw) and time directly affected the water temperature. The study showed that the thermal distribution was stable at 8 and 10 h. At 8 h, the water reached a maximum temperature of 153 °C at Qg = 5 and Qw = 2. When Qg = 5 L/min and Qw = 2 L/min, the receiver wall temperature reached 322 °C, the receiver backplate temperature (Tbp) reached 498 °C, and the gas temperature (Tg) reached 354 °C. At QG and Qw = 20, the water temperature dropped to 46 °C. This showed that the volume flow rate significantly affected the temperature.

The cost of CO2 emissions abatement in a micro energy community in a Belgian context

This paper investigates and quantifies the benefits and the cost of CO2 emissions abatement of a Micro Energy Community (MEC) in a tiny residential cluster of three houses in a Belgian context. A simulation-based comparative analysis is performed of two individual and two MEC concepts, i.e. a reference scenario, an individual electrification scenario, an electricity sharing scenario, and an energy community scenario. A deterministic dynamic white-box modelling approach, including optimal control, is used, considering heat for space heating and domestic hot water, and electricity for electrical appliances. The energy system that achieves the greatest emission reduction at the lowest cost, has a collective heat pump and a photovoltaic installation sized based on the plug load demand. This system reduces the annual CO2 emissions by 11.48 tons at a cost of 179 EUR/ton CO2 considering 2021 dynamic retail electricity prices with a median of 251 EUR/MWh and a fixed retail gas price of 64 EUR/MWh. However, the results are strongly dependent on the gas-electricity price ratio. The highest value of the retail gas price in 2021 leads to a negative CO2 emissions abatement cost of 154 EUR/ton CO2, putting energy community concepts on the radar for a cost-effective energy transition.

Pengaruh variasi besar butir dan variasi komposisi bahan terhadap kinerja briket arang tempurung kelapa dan sekam padi

Abundant biomass waste is often thrown away. Careless disposal of waste will have a negative impact on environmental quality. Research regarding variations in composition and grain size of biomass waste charcoal briquettes on briquette performance is feasible. The aim of the research is to obtain briquettes that have high performance. The research method used was experimental research, coconut shell charcoal and rice husk charcoal, made in sizes 20 mesh, 60 mesh and 100 mesh. Then mixed with 15% starch adhesive with variations in the composition of coconut shell charcoal (TK): rice husk charcoal (SP), namely: I (75%:25%), II (50%:50%) and III (25%:75% ), After printing, the biket is dried in the sun and in the oven until it reaches a moisture content of (14-15)%. After the briquettes are dry, the heating value, flame duration and water boiling time are tested. In the calorific value test, the greater the composition (TK), the greater the calorific value produced. The highest heating value of 5937 kcal/kg was obtained from composition I, mesh 60 and the lowest heating value of 3714 kcal/kg was obtained from composition III mesh 60. The shortest flame duration of 1386.6 seconds occurred in mesh 20 composition III and the longest flame duration was 1933.2 seconds. obtained on mesh 100 composition I. In the Boilling Time test, it was found that the larger the grain size and the greater the composition of the coconut shell charcoal mixture in bioarang briquettes, the faster the water boiling time.

Acoustics of wet porous media with evaporation/condensation

This paper investigates acoustic wave propagation in wet rigid-frame porous media accounting for evaporation and condensation. At equilibrium, the solid walls are covered by a thin water film, and water vapor in the air is at its temperature-dependent saturation pressure. Small acoustic perturbations cause water to vaporize or condense, which together with the reversibility of the phase change, lead to a linear problem where the usual local poro-acoustics physics is enriched with the (i) Clapeyron relation linking liquid-wall temperature, vapor pressure, and latent heat of vaporization, (ii) latent heat transfer in the solid frame, (iii) diffusion equation for water vapor in air, and (iv) water vapor's equation of state. The equilibrium temperature highly influences the vapor concentration and the physical parameters of saturated moist air. Using the two-scale asymptotic homogenization method, it is shown that the dynamic permeability is determined similarly to classical porous media, while the effective compressibility is modified by evaporation/condensation and the equilibrium temperature. This modification is influenced by vapor mass and heat flows associated with phase changes through a local fully coupled heat transfer and water vapor diffusion problem, with specific boundary conditions at the gas–water interface. The analysis identifies dimensionless parameters and characteristic frequencies defining the upscaled model's features. Depending on equilibrium temperature, the theory qualitatively and quantitatively determines the characteristics of acoustic waves propagating through the media. The results are illustrated and discussed with analytically developed models.

Influence of supply temperature and booster technology on the energetic performance and levelized cost of heat of a district heating network with central heat pump

The development of new low-temperature district heating networks in existing urban areas can accelerate the replacement of fossil-fuel-based heating systems by collective heating using electricity or renewable heat sources. Buildings can either be connected to the network in their current, non-refurbished state for rapid deployment or be refurbished before connection to achieve maximum energy efficiency. To assess the difference between these two strategies, this paper examines eight low-temperature district heating concepts with central heat pump, comparing their energy use and levelized cost of heat. The study includes four scenarios for each strategy, considering supply temperatures ranging from 10 °C to 75 °C. Heat pumps or electric heaters are used as booster technology when the network supply temperature is too low for space heating or domestic hot water purposes. The use of booster heat pumps shows the highest seasonal coefficient of performance for both refurbished (4.61) and non-refurbished buildings (3.43). However, booster technologies result in the highest levelized cost of heat, driven mainly by the high investment cost of the network and booster units. Lowest levelized cost of heat of 213 €/MWhth is obtained for non-refurbished buildings at 75 °C and 297 €/MWhth for refurbished buildings at 55 °C without boosters.

A mass-coupled hybrid absorption-compression heat pump with output temperature of 200 °C

Heat pump technology is a promising solution for energy saving and emission reduction in industry. However, current technologies with limited temperature lift are not sufficient to meet the industrial heat demands. Aiming at efficient heat supply over 200 °C, this work proposes a hybrid absorption-compression heat pump cycle with mass coupling between LiBr-water type II absorption heat pump and water vapor compression heat pump, which could reduce the working pressure of compressor. Water injection is applied in the compressor for performance improvement. Detailed performance analysis is carried out for the hybrid heat pump cycle, showing an optimized COP of 3.01 under the temperature lift from 150 °C to 200 °C. Besides, the proposed system is capable of achieving temperature lift of 50 °C for heat source between 100 °C and 164 °C. Greater application superiority occurs at higher temperature output. The proposed cycle broadens the working domain of heat pump.

Experimental investigation of single slope solar still for culinary wastewater treatment

Solar still desalination (SD) offers a sustainable method for purifying contaminated water, despite its productivity limitations. This study proposes an effective treatment process for culinary wastewater (CWW), multilayer-filtered culinary wastewater (MFCWW), and borewell water. We conducted a comprehensive experimental analysis comparing key SD characteristics, including evaporative heat transfer, efficiency, productivity, exergy, and water quality parameters, across these water sources. Our findings reveal that integrating multilayer filtration with CWW significantly improves efficiency, productivity, turbidity reduction, and hardness removal compared with untreated CWW. Notably, MFCWW has emerged as the most promising modification, demonstrating enhanced solar still performance over conventional SD processes. This study highlights the potential of combining multilayer filtration with solar desalination as an innovative approach to improve water purification outcomes, particularly for culinary wastewater treatment.

دراسة عملية لاداء سخان ماء شمسي ذو الدوران الطبيعي المتصل على التوالي

This research paper presents an experimental study on the performance of a natural circulation solar water heater system with two typical collectors connected in series. The paper provides a comprehensive analysis of the system's thermal performance under different load conditions, including no-load, intermittent, and continuous load. Mean storage tank, solar collector means plate (the left) temperature and thermosyphon flow rate in a vertical tank were measured. Results showed that there was variation in solar water tank and collector plate temperature under load and no-load conditions. Analysis of thermal performance of the system was conducted for each condition. The highest plate temperature (100 ˚C or even more) with no circulation of both collector and load conditions, indicate the high quality of the solar collectors even during the cold season. The collector’s arrangement in series connection is of highest gain in energy and higher storage tank mean water temperature. Several characteristic equations obtained to represent the performance of the present natural circulation system under collector connection arrangement in series. In fact, when large amount of hot water was required for a certain purpose (Industrial sector for example - MSF plant or central heating), multiple collectors are to be deployed in series and in parallel to produce the required amount (quantity) and desired temperature (quality) at the same time. Key words: Thermosyphon solar water heater, storage tank profile temperature, Solar Water Heaters (SWHs), instantaneous efficiency, collector flow factor, collector efficiency factor, collector heat removal factor