Use Of Hot Water Research Articles

Studies of solar air conditioning system based on triple effect refrigeration

A solar powered air-conditioning system designed for heating and cooling was put into operation and studies regarding the same triple effect refrigeration through solar thermal energy was carried out. Water, lithium bromide and other chemicals were used in the vapor absorption machine. Chiller having a capacity of 100kw i.e. 30TR was operated on the temperature of 210 0C obtained from solar field depending upon the solar radiations. This is the main part of the whole system because the heat produced by the solar field is used here for converting it into the chilling effect. The generator design of the machine allowed the use of hot water in the temperature range of 140-210 0C. The measured volumetric flow rate of hot water delivered by generator pump was ranging from 2 to 5.6m3/h.

Analysis of monthly and daily profiles of DHW use in apartment blocks in Norway

Profiles of domestic hot water (DHW) use give valuable information for achieving energy saving in buildings. In this article, analysis of monthly and hourly profiles in apartment blocks in Norway was performed. The aim was firstly to identify influencing factors on DHW use and afterwards to define typical DHW use profiles. Due to availability, two different data samples were used for monthly and hourly analysis. Monthly data from 49 apartments showed that approximately 30% of DHW was used in kitchens and the rest 70% in bathrooms. The influence of apartment sizes on DHW use was tested based on monthly profiles. Monthly profiles for three categories of apartments with 33 m2, 51-52 m2, and 68-72 m2 floor area were developed. Cluster analysis allowed us to identify profiles for three groups of apartments with a typical number of residents. In addition, for comparison purpose, DHW hourly profiles in two social housings and two housing cooperatives were investigated. These profiles indicated that there was a difference in when DHW was used in these two types of buildings, with a higher daytime DHW use in social housing. Finally, the measured DHW heat use profiles are compared with the profile in the national standard.

Bayesian Calibration with Augmented Stochastic State-Space Models of District-Heated Multifamily Buildings

Reliable energy models are needed to determine building energy performance. Relatively detailed energy models can be auto-generated based on 3D shape representations of existing buildings. However, parameters describing thermal performance of the building fabric, the technical systems, and occupant behavior are usually not readily available. Calibration with on-site measurements is needed to obtain reliable energy models that can offer insight into buildings’ actual energy performances. Here, we present an energy model that is suitable for district-heated multifamily buildings, based on a 14-node thermal network implementation of the ISO 52016-1:2017 standard. To better account for modeling approximations and noisy inputs, the model is converted to a stochastic state-space model and augmented with four additional disturbance state variables. Uncertainty models are developed for the inputs solar heat gains, internal heat gains, and domestic hot water use. An iterated extended Kalman filtering algorithm is employed to enable nonlinear state estimation. A Bayesian calibration procedure is employed to enable assessment of parameter uncertainty and incorporation of regulating prior knowledge. A case study is presented to evaluate the performance of the developed framework: parameter estimation with both dynamic Hamiltonian Monte Carlo sampling and penalized maximum likelihood estimation, the behavior of the filtering algorithm, the impact of different commonly occurring data sources for domestic hot water use, and the impact of indoor air temperature readings.

Energy and Water Monitoring for a Large Social Housing Intervention in Northern Italy

In recent years, the awareness of the problem of the performance gap and rebound effect extends the interest in assessing the real operation of buildings, in assessing how buildings match users' needs once they are occupied and in understanding how occupants’ behavior affects the actual building performance. The paper discusses the case study and presents the results of a monitoring campaign of two years of occupancy of a large social housing intervention recently built near Milan, for a total of 152 flats. Data about the thermal energy consumption for heating and cooling, the domestic hot and cold water use and the occupants’ intervention on controlling devices are assessed and presented. The case study is representative of the actual design and construction of high performing multi-family buildings in Italy. All the buildings are class A rated, very highly insulated and ventilated with centralized mechanical ventilation systems with thermodynamic heat recovery. Centralized water-to-water heat pumps supply hot and refrigerated water for heating and cooling and domestic hot water as well. A building monitoring system is installed, able to track energy and water consumption, factors influencing the energy consumption not related to the building characteristics (weather data, operational setting) as well as the overall building performance data. The results show unexpected high energy and water consumption and moreover a large variability of the energy and water consumption pattern among the dwellings and between the years due to the significant influence of the occupants’ behavior and habits.

Diagrams of seasonal and daily hot water consumption by apartment buildings (ab) in the moscow region

The article presents an analysis of hot water consumption in apartment buildings of the Moscow region. This study was conducted based on monitoring actual data on hot water consumption by apartment buildings (AB) in Moscow and the Moscow region. The results were used to develop a computational model for the daily use of hot water in apartment buildings.

Energy consumption for domestic hot water use in Norwegian hotels and nursing homes

Domestic Hot Water (DHW) production constitutes a significant proportion of the energy demand of modern buildings, and as the building envelope is improved the share increases. This article discusses the results from a measurement campaign in Norwegian hotels and nursing homes. The energy demand for DHW and distribution heat losses for 3 hotels and 3 nursing homes are shown. The results show that number of bedrooms is a better parameter for describing DHW consumption than sqm of heated floor area. There are large variations in the measured distribution losses, mainly due to malfunctioning of the hot water circulation system. For nursing homes, the measured energy consumption is significantly lower than the normative profiles, which can have large impact on the requirements for the design of the building heating system. For hotels, the measured energy consumption is in the range of the normative profiles.

Environmental life cycle assessment and techno-economic analysis of domestic hot water systems in China

In this study, a cradle-to-grave life cycle assessment was conducted on several typical domestic hot water systems across five climatic regions of China. Variations of the climate and energy supply in these regions and the energy efficiency grade of domestic hot water systems were also taken into consideration. The results suggest that evacuated tube solar systems are highly energy-efficient and low-cost, except in the region with the weakest solar radiation. Electric systems are extremely energy-intensive and uneconomical for domestic hot water use, although they have the least human and ecological toxicity potentials. Solar and air-source energy systems save energy; however, they use more materials and cause more human and ecological toxicity. From the severe cold region to the hot summer and warm winter region, the heat load of domestic hot water increases by 59%, resulting in an increase of 58–230% in primary energy demand. Accordingly, the environmental impacts of domestic hot water systems increase in varying degrees; however, few impacts decrease due to the different emission factors of different power grids. The raw materials used in the manufacture of domestic hot water systems and the energy required for the use of the systems are the most important contributors to all environmental impacts. The scenario analysis indicates that 24.5% of the primary energy demand and 25.7% of greenhouse gas emissions owing to domestic hot water use in China can be reduced by improving the energy efficiency, prompting the use of renewable energy sources, and reducing the usage of materials for domestic hot water systems, as the human and ecological toxicity potentials will increase by 0.1% and 10%, respectively, due to the increasing use of certain materials.

A unified probabilistic model for predicting occupancy, domestic hot water use and electricity use in residential buildings

A novel strategy that combines separate probabilistic models developed by other researchers into a unified model for generating schedules of active occupancy, domestic hot water (DHW) use, and non-HVAC electricity use in multiple residences with a 10-min resolution for every day of the year is described. A variety of new model functions are introduced in order to generate stochastic predictions for each of numerous residences at once, to enforce appropriate variability of behaviors between dwellings and to ensure that domestic hot water and electricity use are coincident with occupancy. The separate models used in this paper were previously developed for the US and the UK; in the unified model, scaling factors were added to these models to adjust the predictions so as to better agree with national aggregated data for Canada. The unified model was validated with measurements of domestic hot water use and electricity consumption from the 40 residential units of a social housing building in Quebec City, Canada. The behavior of occupants in the case study building was simulated 100 times in order to validate the outputs of the unified model. Goodness-of-fit tests applied to each of these simulations showed that the fit between simulated and measured dwelling-per-dwelling distributions was acceptable for 97% of the DHW consumption profiles and for 92% of the electricity consumption profiles. However, there remain discrepancies between simulations and measurements, such as an overestimation of the DHW and electricity consumption in the morning.

Thermodynamic analysis of waste heat recovery of aluminum dross in electrolytic aluminum industry

ABSTRACT In order to recover the waste heat of aluminum dross and carbon resource in carbon residue, the waste heat recovery process of aluminum dross by coupling of physical and chemical method was proposed. In this process, waste heat in the high-temperature range was recovered by carbon residue gasification reaction and waste heat in the low-temperature range was recovered by physical method (PM). Enthalpy and exergy analysis of PM and physical–chemical coupling method (PCCM) processing the aluminum dross was performed by thermodynamic compass method. Sensible heat of aluminum dross can be recovered by PM, but exergy efficiency is 20.4%. And the exergy loss (EXL) is 429 MJ. A lot of hot water is produced by this method, but the use of hot water is limited. The exergy efficiency for PCCM is 38.4% in System 2(a) and 51.2% in System 2(b), respectively. Compared with the PM, the EXL of PCCM is lower, and the exergy efficiency is higher. Each ton of aluminum dross can produce 47.11 m3 CO. in System 2(a) and Each ton of aluminum dross can produce 56.88 m3 CO and H2 in System 2(b). The carbon resources in carbon residue are effectively utilized. Comparing with the energy level of chemical reaction, the influence of specific temperature for exergy efficiency is more significant during the physical–chemical coupling of waste heat recovery process.

Influence of formic acid and iron oxide nanoparticles on active hydrogenation of PAHs by hot compressed water. Isotope tracing study

Use of hot compressed water (HCW) as a reaction medium to enhance conversion efficiency of polyaromatic hydrocarbons (PAHs) to lighter products is an important topic in green chemistry, where hydrogenation and ring opening of PAHs are crucial for tar removal and heavy oil upgrading with less coke. In this study, the influence of HCW on the conversion of coronene (super benzene) as model molecule of PAHs with 7-ring is examined. A series of agents, such as cheap iron oxide NPs (α-Fe2O3) as an oxygen-donor, formic acid (CHOOH) as hydrogen-donor, and their physical mixtures, are used. Pure deuterium oxide (D2O) is also applied instead of H2O to track the hydrogenation from HCW. The influences of water density; reaction temperature, reaction time, and amount of catalyst loading on conversion of coronene and yield of coke are studied. The reaction in the presence of D2O as control experiment shows minor H/D exchange during the reaction process stating that water itself has no effect on hydrogenation of coronene. In the presence of agents (iron oxide, formic acid and their mix), however, outstanding synergistic effect occurs and water could be used as a green and efficient medium for hydrogenation and enhancing the conversion of coronene. In summary, the isotope tracing experiments reveals that hydrogenation from HCW only cape the double-bond carbon which belongs to the PAHs rings (CH), instead of hydrogenation of created alkyl groups with single-bond carbon (CH). This issue indicates the strong impact of active hydrogen from condensation reaction on hydrogenation of PAHs, which elaborated at the cost of made coke.

Determination of the specifications and quantities of pollutants present in water discharged from oil plant and their treatment methods

Water pollution is an important environmental problem at present and has a direct impact on the lives of individuals, families and society. Water pollution is produced from several industrial processes. One of these processes is the making vegetable oils, where the polluted water is produced by the refining of vegetable oils, there is also contaminated water resulting from the process of bleaching vegetable oil, there is another pollution of the water produced by the process of removing the smell of vegetable oil and there is also pollution of water resulting from heat exchangers where the use of cold or hot water. In this research, were used natural and chemical materials, different concentrations and different weights to reach the best results. The treatment process is done in two phases, the first by adding the following substances (alum, calcium hydroxide alkaline and concentrated sulfuric acid) in different quantities to the polluted water and then leaving a period of time after it is separated from the sediment method. After treatment, (pH), residual Chlorine (cl), bioactive oxygen (BOD5), Oils and Greases (O & G) and phosphate (PO4) are measured. The second phase of the water is adsorbed by activated carbon adsorption for the removal of chlorine from the water (a class of halogens) which is strongly adsorbed by activated carbon. First, (pH), (BOD5), (O & G), and phosphate (PO4) have been controlled within the allowable limits, while the residual chlorine (cl) is much higher than the maximum limits, where it was treated in the second stage, up to the surveyed boundary before it was put into the river water.

Experimental investigation of an adsorption air-conditioner using silica gel-water working pair

Compared to adsorption chiller, adsorption air-conditioner can get significant benefit of less cost and complexity when it directly provides chilled air for air-conditioning. Hence, adsorption air-conditioner is suitable for residential solar cooling application. A 3 kW adsorption air-conditioner using silica gel-water working pair is designed and manufactured and its performance is fully tested under different conditions. The experimental results show that cooling power and COP can reach 3.98 kW and 0.632, respectively, without obvious periodic fluctuation of chilled air outlet temperature and relative humidity. Smaller hot water flow rate can help to reduce unmatching between heating and cooling operation of adsorption bed. Optimal half cycle time of this adsorption air-conditioner is found to be 750 s. COP of adsorption air-conditioner is generally larger than that of adsorption chiller which provides chilled water because of higher evaporation temperature. Besides, cooling water outlet temperature can reach 39.9 °C which can meet the requirement of domestic hot water use. So that adsorption air-conditioner can be used for cooling and heating cogeneration in a residential solar cooling application and achieve good performance.

Meeting the demand: geothermal heat supply rates for an urban quarter in Germany

Thermal energy for space heating and for domestic hot water use represents about a third of the overall energy demand in Germany. An alternative to non-renewable energy-based heat supply is the implementation of closed and open shallow geothermal systems, such as horizontal ground source heat pump systems, vertical ground source heat pump (vGSHP) systems and groundwater heat pump systems. Based on existing regulations and local hydrogeological conditions, the optimal site-specific system for heat supply has to be identified. In the presented technical feasibility study, various analytical solutions are tested for an urban quarter before and after building refurbishment. Geothermal heat supply rates are evaluated by providing information on the optimal system and the specific shortcomings. Our results show that standard vGSHP systems are even applicable in older and non-refurbished residential areas with a high heat demand using a borehole heat exchanger with a length of 100 m or in conjunction with multiple boreholes. After refurbishment, all studied shallow geothermal systems are able to cover the lowered heat demand. The presented analysis also demonstrates that ideally, various technological variants of geothermal systems should be evaluated for finding the optimal solution for existing, refurbished and newly developed residential areas.

Alternative hydronic pavement heating system using deep direct use of geothermal hot water

Researchers have studied and well documented several alternative snow-melting and de-icing systems. In addition to the snow-melting efficiency of such systems, they are considered to be more environmentally friendly than traditional mechanical or chemical de-icing procedures and more economical than some other alternative snow-melting methods. The most important factor for a hydronic heating system is the heat source. In western North Dakota, six aquifers have been identified in the Williston Basin that can provide geothermal hot water for direct use. Ancillary to these aquifers, co-production wells used in the oil industry may also provide hot water for use in a hydronic heating system. Given the availability of these aquifers and co-production wells, the focus of this study is the numerical analysis (using a finite element method) of a piped hydronic pavement heating system. The analysis results are examined in terms of available scenarios for the direct use of geothermal hot water that consider water temperature, volumetric flow rate, and the heat requirements for weather conditions in western North Dakota. This paper presents and discusses the results in terms of the temperatures of the heated pavement and the outlet temperatures of water after it has circulated through embedded pipes.

Experimental Measurements of Hot Water Stratification in a Heat Storage Tank

The contribution focuses on the experimental measurement of the method of accumulation of hot water with its temperature layer in storage heaters using elementary cone elements. The basic principle of these elements is the automatic temperature distribution of water temperatures according to the temperature and flow rate for a specified storage time of heat energy from different heat sources in the heating system and hot water preparation. The thermal stratification in the stratified storage tank ensures maximum energy savings of up to 60% compared to standard storage tanks. The values of measurement were processed in a simulation fashion and compared to the real measured values. The aim of the experiments was to prove maximum energy savings and to determine the actual efficiency of elementary elements in stratification storage heaters with different heat sources. Storage of heat energy and its use is an important way of energy saving systems under Directive 2010/31 / EU of the European Parliament and of the Council on the energy performance of buildings. Stratification storage systems are used for different types of heating and also for domestic hot water preparation in all types of buildings. Their importance is evident when there is a need for efficient use of thermal energy in low-energy buildings and buildings with zero energy consumption, where they can be used for common use of hot water (50 - 60 °C) with different temperatures for heating (e.g. floor heating, convective heating, etc. ranging from 25 to 60 °C). The most efficient way is to combine stratified heat storage tanks with solar heating systems, heat pumps, or boilers. Every building must be assessed individually in terms of requirements for heating and the method of domestic hot water preparation and distribution. Furthermore, when engineering a heating system for any building, the use of a renewable energy source has to be taken into consideration too.

Analysis of energy signatures and planning of heating and domestic hot water energy use in buildings in Norway

Widespread introduction of low energy buildings (LEBs), passive houses, and zero emission buildings (ZEBs) are national target in Norway. In order to achieve better energy performance in these types of buildings and successfully integrate them in energy system, reliable planning and prediction techniques for heat energy use are required. However, the issue of energy planning in LEBs currently remains challenging for district heating companies. This article proposed an improved methodology for planning and analysis of domestic hot water and heating energy use in LEBs based on energy signature method. The methodology was tested on a passive school in Oslo, Norway. In order to divide energy signature curve on temperature dependent and independent parts, it was proposed to use piecewise regression. Each of these parts were analyzed separately. The problem of dealing with outliers and selection of the factors that had impact of energy was considered. For temperature dependent part, the different methods of modelling were compared by statistical criteria. The investigation showed that linear multiple regression model resulted in better accuracy in the prediction than SVM, PLS, and LASSO models. In order to explain temperature independent part of energy signature the hourly profiles of energy use were developed.

The Possibilities of Using Broadleaf Cattail Seeds (Typha latifolia L.) as Super Absorbents for Removing Aromatic Hydrocarbons (BTEX) from an Aqueous Solution

Sorption of oil-related products (including mainly the propellants) is the very basic process that counteracts spreading these types of pollution into environment. Plenty of synthetic substances (including the monoaromatic hydrocarbons) are both from the surface and underground waters. The aim of this study was to present the research’s results on the possibilities of using the broadleaf cattail (Typha latifolia L.) seeds as a sorbent of monoaromatic hydrocarbons from an aqueous solution. In order to increase sorptive capacity, the seeds biomass was submitted for the process of mercerizing in diversified time and temperature in water and the NaOH solution. The removal of benzene, toluene, ethylbenzene, o-xylene, m-xylene and cumene was carried out by means of the “batch method”. All the conducted experiments have shown a high sorption level of the analysed pollutions from an aqueous solution. The best sorptive qualities appeared in the seeds drenched in 80 °C water for 4 h (W) 97 g/kg, what was 9.06% more absorbed hydrocarbons in comparison to the control sample (C) and 26.8% more than the smallest seeds drenched in NaOH for 240 min. in the temperature of 80 °C (N). The process of the seeds mercerizing that was conducted with the use of hot water appeared to be most effective, but seeds without mercerisation (C) is actually the material which absorbs the least amounts of energy for preparation and had quite good sorption capacity too.

Performance study of solar photovoltaic-thermal collector for domestic hot water use and thermochemical sorption seasonal storage

To maximise the utilisation of solar energy and improve the solar fraction for domestic applications, this paper explored the potential of the hybrid solar Photovoltaic/Thermal (PV/T) collector integrated with a thermochemical sorption thermal storage system. The thermal output was used to provide domestic hot water or stored over seasons in the England city of Newcastle upon Tyne. The performance of the water-cooled PV/T collectors with or without an air insulation layer between the glass cover and the Photovoltaic (PV) cell was compared. The electrical power generation model of the PV cell developed in MATLAB was coupled with a Computational Fluid Dynamics (CFD) model to simulate the simultaneous generation of electrical and thermal energy. The one-diode model was used to simulate the electrical production of the PV cell with the new correlations of the series resistance and the shunt resistance proposed in this work, so that the accuracy of dynamic performance simulation can be improved especially in the cases with relatively higher PV cell temperature. The water outlet temperature was studied at 100 °C to meet the heat supply requirement of the sorption cycle using the working pair strontium chloride-ammonia. It was found that the PV/T collector with air gap could produce 28 L hot water per day per m2 collector (L/(day·m2)) with the electric efficiency of about 10% if the water outlet temperature was required at 100 °C; in contrast, around 133 L/(day·m2) was produced with the electric efficiency of 13% when the water outlet temperature at 40 °C. The PV/T collector without air gap was not competent for the applications studied in this work especially in cold regions. The application case studies suggested that an installation of 26 m2 air-gap PV/T collectors integrated with the strontium chloride-ammonia thermochemical sorption storage system can fully satisfy the annual hot water demand of an ordinary single household in Newcastle upon Tyne with 100% solar sources, and cover at least half of the annual electricity consumption.

Use of hot water, combination of hot water and phosphite, and 1-MCP as post-harvest treatments for passion fruit (Passiflora edulis f. flavicarpa) reduces anthracnose and does not alter fruit quality

This research aimed to evaluate the effectiveness of hot water (43–53 °C · 5 min−1; 47 °C · 2–6 min−1), 1-methylcyclopropene (1-MCP) at 50–300 nL L−1 and a combination of hot water (47/49 °C · 5 min−1) and phosphite (40% P2O5 + 20% K2O; 40% P2O5 + 10% Zn) in anthracnose control and the effect on fruit quality [fresh weight loss (FWL—%); pH, total soluble solids (TSS—°Brix), and titratable acidity (TA = % citric acid (CA)] of passion fruit (Passiflora edulis f. flavicarpa) at the post-harvest stage. When the fruits were in the stage of 0% dehydration and fully yellow peels, they were disinfested and inoculated with Colletotrichum gloeosporioides. They were then subjected to the above mentioned treatments; this was followed by incubation for 120 h. The diameter of the disease lesions was monitored daily. After the incubation, a physico-chemical analysis was performed. Hot-water treatment resulted in disease reduction at 47 and 49 °C for 4 and 5 min. The combination of hot-water treatment at 47 °C (4 or 5 min) and application of the phosphite of K or Zn significantly reduced disease severity in fruits. The 1-MCP treatment reduced anthracnose severity in passion fruit mainly at 200 nL L−1 · 24 h−1. None of the treatments significantly changed the physico-chemical characteristics of the fruit [FWL (2.6–4.1%); pH (3.2–3.5), TSS (8.9–10.9 °Brix), and TA (1.8–2.5% CA)].

Chlorination by-product levels in hot tap water: Significance and variability

People are exposed to chlorinated by-products (CBPs) through the consumption of cold tap water (CTW) (ingestion, inhalation, dermal contact) but also through the use of hot tap water (HTW) in such activities as showering and bathing (inhalation, dermal contact). This study focuses on the impact of residential water heating on CBP levels in tap water. Trihalomethane (THM) and haloacetic acid (HAA) levels were measured in the CTW and HTW of 50 residences located in two distribution systems supplied by chlorinated surface water during summer and winter. Results show important differences between CBP levels measured in cold and hot tap water. However, the magnitude of changes differs according to the specific species of THMs and HAAs, the season, the distribution system and the location within the same distribution system. Residential water heating led to an increase in average THM levels for the two distribution systems studied, which tended to be greater in winter. Residential water heating affected the two main HAA species found in the area studied (dichloroacetic (DCAA) and trichloroacetic (TCAA) acids) differently. In fact, the average DCAA levels increased due to water residential heating while a small change in average levels was observed for TCAA. However, the water heating impact on HAAs (in terms of importance and sometimes of tendency (increase vs. decrease)) may also differed between residences. The influence of seasons on the change in the average DCAA and TCAA levels (in μg/L) from residential water heating was not statistically significant except for TCAA levels in one distribution system. Results show the importance of considering site-specific characteristics of CTW (CBP level, temperature, residual chlorine, etc.) to estimate the levels of CBPs in HTW in CBP exposure assessment studies (and not to generalize for an entire population). The reported data can thus be useful in assessing for exposure to DBPs in epidemiological studies.