Hot Water Installations Research Articles

Utilizing big data to determine the temperature dependency of Legionella in hot water systems

ABSTRACT Domestic hot water installations provide an ideal habitat for Legionella spp. and pose a potential risk of human infection. Heating the water is considered the major preventive measure against Legionella contamination. Our study aimed to understand better the relationships between hot water temperatures and Legionella spp. occurrence within such systems. We utilized routine monitoring data from public and apartment buildings, comprising 292,937 data sets. We employed the analysis of variance, receiver operating characteristic analysis, and relative probability of occurrence to quantitatively assess statistical relationships. In the case of supply flow (SF) and return flow (RF), i.e. near the water heater, water temperature strongly regulates Legionella spp. growth. Below calculated tipping points (SF: 56 °C, RF: 53 °C), the relative probability of Legionella spp. occurrence is 18.7 and 7.5 times higher, respectively. For peripheral samples, the relationship between temperature and Legionella spp. occurrence is less pronounced. Additionally, statistical relationships between central and peripheral temperatures, as well as between central temperatures and peripheral Legionella spp. concentrations within one system, were weak or zero, respectively. Thus, the central temperature regime of hot water systems alone is insufficient to control the occurrence of Legionella spp. in the periphery.

Persistence of viable but nonculturable Legionella pneumophila state in hospital water systems: A hidden enemy?

There is little evidence of the long-term consequences of maintaining sanitary hot water at high temperatures on the persistence of Legionella in the plumbing system. The aims of this study were to describe the persistence and genotypic variability of L. pneumophila in a hospital building with two entirely independent hot water distribution systems, and to estimate the thermotolerance of the genotypic variants by studying the quantity of VBNC L. pneumophila. Eighty isolates from 55 water samples obtained between the years 2012–2017 were analyzed. All isolates correspond to L. pneumophila serogroup 6. The isolates were discriminated in four restriction patterns by pulsed-field gel electrophoresis. In one installation, pattern A + Aa predominated, accounting for 75.8 % of samples, while the other installation exhibited pattern B as the most frequent (81.8 % of samples; p < 0.001). The mean temperature of the isolates was: 52.6 °C (pattern A + Aa) and 55.0 °C (pattern B), being significantly different. Nine strains were selected as representative among patterns to study their thermotolerance by flow-cytometry after 24 h of thermic treatment. VBNC bacteria were detected in all samples. After thermic treatment at 50 °C, 52.0 % of bacteria had an intact membrane, and after 55 °C this percentage decreased to 23.1 %. Each pattern exhibited varying levels of thermotolerance. These findings indicate that the same hospital building can be colonized with different predominant types of Legionella if it has independent hot water installations. Maintaining a minimum temperature of 50 °C at distal points of the system would allow the survival of replicative L. pneumophila. However, the presence of Legionella in hospital water networks is underestimated if culture is considered as the standard method for Legionella detection, because VBNC do not grow on culture plates. This phenomenon can carry implications for the Legionella risk management plans in hospitals that adjust their control measures based on the microbiological surveillance of water.

The Influence of Nusselt Correlation on Exergy Efficiency of a Plate Heat Exchanger Operating with TiO2:SiO2/EG:DI Hybrid Nanofluid

This paper studies how the correlation with the Nusselt number affects the final result of the efficiency, ε, and exergy efficiency, ηex, of a chevron-type gasketed plate heat exchanger, which is installed in a typical small solar installation dedicated to single-family housing; the solar fluid is a TiO2:SiO2/EG:DI hybrid nanofluid with concentrations from 0% to 1.5% vol. The experimental model assumes constant flow of the solar fluid and varies on the domestic hot water side—from 3 lpm to 6 lpm. The inlet temperatures are 30 °C and 60 °C on the cold and hot sides of the heat exchanger, respectively. Of the six analysed correlations that showed similar trends, it is concluded that for the assumed flow conditions, geometry, and chevron angle of the plate heat exchanger, one model is the most accurate. The largest difference between the ηex values for a given concentration is 3.4%, so the exergy efficiency is not affected by the chosen Nusselt model by very much. However, the choice of correlation with the Nusselt number significantly affects the efficiency, ε; the difference between the values obtained within a given concentration is more than 40% and depends on the Reynolds number and flow. Most research discusses the scenario with the nanofluid as a coolant. This paper considers the opposite situation in which the solar fluid is a hotter working medium that transfers heat to domestic hot water installation.

Domestic hot-water boilers harbour active thermophilic bacterial communities distinctly different from those in the cold-water supply

Running cold and hot water in buildings is a widely established commodity. However, interests regarding hygiene and microbiological aspects had so far been focussed on cold water. Little attention has been given to the microbiology of domestic hot-water installations (DHWIs), except for aspects of pathogenic Legionella. World-wide, regulations consider hot (or warm) water as ‘heated drinking water’ that must comply (cold) drinking water (DW) standards. However, the few reports that exist indicate presence and growth of microbial flora in DHWIs, even when supplied with water with disinfectant residual. Using flow cytometric (FCM) total cell counting (TCC), FCM-fingerprinting, and 16S rRNA-gene-based metagenomic analysis, the characteristics and composition of bacterial communities in cold drinking water (DW) and hot water from associated boilers (operating at 50 – 60 °C) was studied in 14 selected inhouse DW installations located in Switzerland and Austria. A sampling strategy was applied that ensured access to the bulk water phase of both, supplied cold DW and produced hot boiler water. Generally, 1.3- to 8-fold enhanced TCCs were recorded in hot water compared to those in the supplied cold DW. FCM-fingerprints of cold and corresponding hot water from individual buildings indicated different composition of cold- and hot-water microbial floras. Also, hot waters from each of the boilers sampled had its own individual FCM-fingerprint. 16S rRNA-gene-based metagenomic analysis confirmed the marked differences in composition of microbiomes. E.g., in three neighbouring houses supplied from the same public network pipe each hot-water boiler contained its own thermophilic bacterial flora. Generally, bacterial diversity in cold DW was broad, that in hot water was restricted, with mostly thermophilic strains from the families Hydrogenophilaceae, Nitrosomonadaceae and Thermaceae dominating. Batch growth assays, consisting of cold DW heated up to 50 – 60 °C and inoculated with hot water, resulted in immediate cell growth with doubling times between 5 and 10 h. When cold DW was used as an inoculum no significant growth was observed. Even boilers supplied with UVC-treated cold DW contained an actively growing microbial flora, suggesting such hot-water systems as autonomously operating, thermophilic bioreactors. The generation of assimilable organic carbon from dissolved organic carbon due to heating appears to be the driver for growth of thermophilic microbial communities. Our report suggests that a man-made microbial ecosystem, very close to us all and of potential hygienic importance, may have been overlooked so far. Despite consumers having been exposed to microbial hot-water flora for a long time, with no major pathogens so far been associated specifically with hot-water usage (except for Legionella), the role of harmless thermophiles and their interaction with potential human pathogens able to grow at elevated temperatures in DHWIs remains to be investigated.

Green Buildings in Pursuit of Healthy and Safe Human Living Environment

Abstract Emission of harmful substances into the atmosphere resulting from the combustion of fuels in the energy production process and road traffic intensity are a key determinants of poor air quality in cities and the creation of an unfriendly environment for people to live in, which has a significant impact on their safety and health. The first step to reducing emissions is to reduce energy consumption. The ecological effect resulting from the thermal modernization of existing residential building stock was estimated. Nature-based solutions were proposed to compensate for the lost green areas in favor of gray infrastructure in the form of green roofs and walls. The possibility of improving environmental conditions by introducing this type of solutions into the urban tissue was assessed. Depending on the type of vegetation, one m2 of green cover is able to absorb an average of 2.3 kg of CO2 and 0.2 kg of particulate matter from the air per year. Renewable energy sources are an important element of green buildings. Heat pump may be the most advantageous solution in minimizing emissions combined with low operating costs. Obtaining energy from geothermal sources would be equally beneficial in terms of reducing emissions, but there are risks changes in groundwater levels or soil damage. Solar energy is one of the leading renewable energy sources, especially in hot water installations, where it is possible to reduce energy consumption by up to 50%.

A mixed integer linear programming-based simple method for optimizing the design and operation of space heating and domestic hot water hybrid systems in residential buildings

The hybridization of energy systems is based on the combined integration of both renewable and non-renewable technologies and thermal energy storage. These hybrid installations improve cost effectiveness and energy efficiency when they are correctly designed and the operation strategy is suitable. Despite the relevance of achieving the optimal configuration, sizing and control strategy of hybrid thermal systems, there is no simple and generic methodology which allows this type of installations to be optimized in the project phase. In response to this issue, in this work, a mixed integer linear programming-based simple model is carried out with the aim of obtaining the optimal design, sizing and operation of thermal energy systems in residential buildings. To do so, a superstructure is defined that includes the main technologies commercialized for thermal energy systems in buildings. Technical, economic, environmental and legal constraints are determined in the proposed generic model. In order to validate the method, it is applied to a central space heating and domestic hot water installation of a residential building located in a cold climate in Spain. Optimal solutions are obtained considering three different perspectives —economic, environmental and multicriteria— and are compared to the current installation. According to the results, the overall cost of the economic optimal configuration is reduced by 15%, whereas the greenhouse gas emissions decrease by 56% in the environmental optimal solution. It is thus demonstrated that the proposed generic and simple model is a useful tool for determining the optimal hybridization of the plant and for analysing the technical, economic and environmental feasibility of these systems in the project phase.

Energy Consumption by DHW System with a Circulation Loop as an Energy Efficiency Component, Based on an Example of a Residential Building

In the EU countries, almost 50% of the produced energy is used in residential buildings. More than 25% of this energy is used to produce domestic hot water, of which almost 80% is used to heat water in domestic hot water circulation systems. This is due to high expectations on the part of residents based on their comfort, in particular regarding the supply of heat for heating and domestic hot water. In the course of their long-term research conducted on real systems, the authors confirmed that the operation of domestic hot water distribution systems causes significant costs, mainly due to heat losses. Therefore, typical variants of energy optimization of such systems were analyzed. Tests have shown that selected solutions, such as the use of control automation, are not sufficient, and recommended additional thermal insulation may not be applicable due to technical reasons. With an aim of finding a solution to the problem, the publication analyzes operational data from an existing heat source and domestic hot water circulation system in a residential building. On the basis of these analyses, a solution was proposed to reduce energy consumption within the installation by means of its hydraulic optimization. The reduction of heat losses in domestic hot water installation by means of a method presented by the authors is estimated at approximately 20%.

РАСЧЕТНЫЙ АНАЛИЗ ИСПОЛЬЗОВАНИЯ БРОМИСТО-ЛИТИЕВОГО РАСТВОРА ДЛЯ БЫТОВОГО АБСОРБЦИОННОГО ТРАНСФОРМАТОРА ТЕПЛОТЫ

Steam compression installations operating from electric energy are widely used in the world for air conditioning. This type of installation has a number of disadvantages, and therefore a new air conditioning installation has been proposed. Ab-sorption heat transformer is an air conditioning and hot water installation based on the principle of an absorption heat pump. The installation can also be used for heating. The installation is able to use renewable energy sources or utilize the heat of exhaust gases as heat sources: for example, from a heating boiler with a temperature of up to 115 °C. The practical significance of the installation lies in resource conservation and environmental friendliness. The use of this installation will ultimately reduce the consumption of primary fuel and reduce the negative impact on the environ-ment. The paper considers the possibility of using a lithium bromide solution in an absorption heat transformer for resi-dential premises. For this purpose, a number of calculations were carried out, according to the calculation method of ab-sorption refrigerating lithium bromide machines. As a result of the calculations, it was established that the use of lithium bromide solution is satisfactory for use in a household heat absorption transformer. However, in order to achieve greater efficiency, the installation scheme requires refinement.

As a case study, energy analysis application of a hotel business in private sector

In our study, a detailed energy study was carried out in a hotel business, which is a commercial building, energy saving potential was determined, measures that could be taken to increase energy efficiency and reduce energy consumption costs were determined and recommendations were presented. As a result of the measurements of the hot water installation line with the thermal camera, heat losses in the valves and flanges were observed and insulation was recommended. When the investment determined for insulation is made, it is calculated that there will be a decrease of approximately 17% in the annual energy consumption for the water installation. After heating, booster and fire pump motors with efficiency class EFF2 were replaced with IE4 efficiency motors, it is seen there is a 6.9% increase in motor efficiency. As a result of replacing the IE1 class engine used in the cooling system with an IE4 class engine, the engine efficiency is expected to increase by 6.2%. As a result of the replacement of halogen bulbs in the business with LED luminaires, the annual total electricity savings were calculated as approximately 19158.12 kW/year.

Thermal Characterization of Medium-Temperature Phase Change Materials (PCMs) for Thermal Energy Storage Using the T-History Method.

To reduce energy consumption and increase energy efficiency in the building sector, thermal energy storage with phase change materials (PCMs) is used. The knowledge of the thermophysical properties and the characteristics of PCMs (like their enthalpy changes and the distribution of stored energy over a specified temperature range) is essential for proper selection of the PCM and optimal design of the latent thermal energy store (LHTES). This paper presents experimental tests of the thermophysical properties of three medium-temperature PCMs: OM65, OM55, RT55, which can be used in domestic hot water installations and heating systems. Self-made test chambers with temperature control using Peltier cells were used to perform measurements according to the T-history method. In this way the temperature range of the phase transition, latent heat, specific heat capacity, enthalpy and the distributions of stored energy of the three PCMs were determined. The paper also presents measurements of the thermal conductivity of these PCMs in liquid and solid state using a self-made pipe Poensgen apparatus. The presented experimental tests results are in good agreement with the manufacturers’ data and the results of other researchers obtained with the use of specialized instruments. The presented research results are intended to help designers in the selection of the right PCM for the future LHTES co-working with renewable energy systems, waste heat recovery systems and building heating systems.

Develop a solar system to reduce the power usage reduction in sanitary hot water installation for southwest region of Saudi Arabia

In this study, the usefulness of adding a solar system to a domestic hot water supply system (boiler) was investigated. The amount of hot water consumption was determined taking into account hot water usage on workdays and weekends. Considering the amount of global horizontal irradiation 2328.2kwhm2.year for southwest region (Wadi Al-Dawasir) in Saudi Arabia and using transient analysis, the heat gain in collectors was specified at the optimal tilt. The results showed that by adding a solar system (which used water at 30 kghr) the boiler power usage reduced by 21,389 kWh per year. Based on numerical calculations, the higher flow rates in collector (60 and 90 kghr), the lower energy saving (19550 and 18663kWhyear). Dispersing nanoparticles of Pentaethylene Glycol-Treated Graphene Nanoplatelets (GNPs + PEG) into water at 0.025–0.1 vol% led to a superior energy-saving. At 30 kghr, owing to using GNPs + PEG/water at 0.025 vol%, energy saving improved by 1080kWhyear (from 21,389 to 22,469 kWhyear). Loading more nanoparticles resulted to higher energy-saving so that at 0.1 vol%, it was 23,376 kWhyear. Under the best case conditions and owing to using solar system, the boiler energy usage reduced by 26.8% (for water) and 29.3% (for GNPs + PEG/water 0.1 vol%).

Analysis of the Impact of Thermal Rehabilitation on the Heat Demand. Case Study

The article presents a case study on the impact of thermal rehabilitation of buildings heat demand. In order to reduce specific heat consumption and, in general, heat consumption for heating and hot water preparation, measures are needed to rehabilitate and modernize the thermal protection of buildings and heating and hot water installations. The present study aims to determine the influence of thermal rehabilitation of buildings (insulation of exterior walls - in this case) making for this purpose a comparison of the values of thermal requirements before and after the thermal rehabilitation process for a building. Regarding the thermal insulation used in the case study, expanded polystyrene with a thickness of 10 cm was used for the exterior walls and mineral wool for ceiling. The main purpose of the work is to highlight the importance of thermal insulation of buildings mainly in terms of reducing energy costs and maintaining thermal comfort in homes

A Cost-Effective and Efficient Electronic Design for Photovoltaic Systems for Solar Hot Water Production

A significant percentage of energy consumption in buildings is to produce hot water. Photovoltaic solar heating can be considered a clean and renewable energy option—easy to install, silent, and without maintenance—to replace the consumption of fossil fuels used in this process. This paper presents a study that simulates the heating process using thermal electrical resistors powered by photovoltaic solar energy. For this purpose, a solar hot water installation has been set up. This installation consists of a water tank with an electric resistance connected to photovoltaic modules by means of a low-cost experimental electronic conversion system. This electronic system has been developed to avoid the need for inverters or batteries, typical of traditional photovoltaic solar installations. It is an isolated system since it is not connected to the power grid. The photovoltaic solar modules, the tank, and its heating resistance correspond to commercial models. This electronic system has a 95.06% yield, and it operates across the whole irradiance’s daily curve, having verified its operation over several months. Even though this is an experimental electronic device, it is financially viable as the cost of its components is below EUR 60 per kW peak capacity. The results obtained in a proper functioning system are promising, demonstrating the technical feasibility and economic advantages of using this type of isolated photovoltaic system to power heating processes.

Comfort of Domestic Water in Residential Buildings: Flow, Temperature and Energy in Draw-Off Points: Field Study in Two Danish Detached Houses

There is very little knowledge on the occupant actual hot water comfort (temperature and flow), usage practice, and routines (temporal and spatial distribution of hot water usage in a household). This paper describes the results from the total and hot water measurements in two Danish detached houses. The results show that, at the draw-off points, the temperature of 55 °C is never asked by the occupants, not even in the kitchen sink. The domestic water temperature differentiates depending on the function of the draw-off point, with the shower and kitchen taps being most energy- and water-intense. They constitute around 90% of the hot water use in the house. Shower units on average demand for highest temperature (i.e., 35.5 °C to 40.4 °C). Hand washing operates, on average, at temperature between 20.5 °C to 26.5 °C. Average water temperature at the taps located in utility room varies between 23 °C to 26 °C. These in-depth insight in the total and hot water use in two new-built low energy houses, can a) help building professionals designing more efficient hot water installations; b) enhance the research work on energy flexibility buildings by providing knowledge on most energy-intensive draw-off points; and c) facilitate district heating professionals in improving the network performance.

Thermal performance analysis of 28 PVT solar domestic hot water installations in Western Europe

Abstract Hybrid solar PVT has the potential to become a major player in the renewable energy sector, but one of the main barriers is the lack of reliable data due to limited number of monitored PVT hybrid systems with proven thermal performance results. In order to address this issue, a statistical study was realized to analyze in-field performances of twenty-eight hybrid solar domestic hot water installations equipped with innovative non-overglazed PVT collectors in Western Europe (France, Switzerland and Portugal). The results show that PVT technology, more than PV production, is particularly relevant on domestic hot water preheating, with a monthly average of daily maximal temperature (Tmean) in the panels reaching above 45 °C during 5 months in the year. The results also demonstrate the robustness of the non-overglazed PVT collector, as the highest stagnation temperature was always measured below 74.5 °C, which is very safe in terms of risk of overheating and effect on PV performance. The twenty-eight hybrid solar domestic hot water data base allows the quantify the main deviation compared to the classical simplified production simulations.

Performance of solar hot-water installations from roof-constructed solar collectors integrated with a central heating supply for tobacco curing

In view of the abundant solar energy available during the tobacco curing season, a solar hot-water installation to provide auxiliary heating for bulk tobacco-curing operations was developed, based on the original concept of a boiler-driven central heating supply that transported hot water over short distances by pipeline, using solar collectors connected in parallel and installed on the unoccupied flat roofs of 20 curing barns. The results showed that daily solar conversion efficiency ranged from 65% to 67%. During the tobacco curing period from 10:00 hours to 14:00 hours each day, in sunny or partly cloudy weather, heating water temperatures exceeding 75?C were automatically derived for use in the bulk curing barns needed. Use of solar energy as a substitute for coal fuel in tobacco curing, in conjunction with precise automatic control, enabled solar energy to account for 18.4% of the total curing energy consumption in this study. Through comparative analysis, the use of solar hot-water installations can help the local tobacco industry to reduce absolute carbon emissions by more than 10% at the experimental location in the pay-back period.

Reliability and optimal replacement interval of flexible hose assemblies in drinking water installations

The paper presents theoretical considerations and questionnaire examinations concerning reliability and replacement interval of flexible hose assemblies for washbasins, sinks and water closets. The topic is vitally important for providing home safety. The impact of operational temperature on durability of elastomeric tube was theoretically assessed. Questionnaire examinations covered 356 hoses installed in a block of flats in Poznan (Poland) and detached houses. The analyzed period of hoses’ operation was 11 years or less in the case of earlier failure. During that time 41 hoses (approximately 12%) had failed. Reliability functions were obtained separately for cold and hot water installations. It was found that flexible hose assemblies for hot water were less reliable than those for cold water. The optimal time to replace hoses was estimated as 6–7 years.

Detection of pathogenic bacteria in hot tap water using the qPCR method: preliminary research

Drinking water should be safe for health and free from amounts of pathogenic microorganisms and parasites posing a threat to human health. In recent years, particular attention has been paid to the threat associated with the operation of hot water installations, potentially providing favourable conditions for the development of bacteria of genera Legionella and Escherichia. Such bacteria are commonly found in the natural environment, but should not reach the consumers’ taps. In this experiment, hot water samples were collected from six public buildings, and the detection of pathogenic microorganisms, namely Legionella spp., Legionella pneumophila, and Escherichia coli bacteria, was performed by means of qPCR analysis. The sequences specific for these bacteria were quantified with TaqMan probes in total DNA extracts of the hot tap water samples. Bacteria of the Legionella spp. type were detected at five sampling sites in the range from 4.52 to 15.59 genomes/mL of hot tap water. Legionella pneumophila was detected at four sampling sites in the range from 0.98 to 11.99 genomes/mL. E. coli was recorded at four sites, but in quantities around 0.00 genomes/mL (less than one genome/mL). This preliminary research points to the need to use molecular techniques as an additional source of information in standard water analyses to obtain shorter detection time and more accurate results.

The Main Changes Made to the Building Codes and Regulations of the “Solar Hot Water Installations” to Increase Energy Efficiency of Projected Solar Power Plants

The progress of work on the revising of building codes and regulations of the “Solar Hot Water Installations”, operating in the territory of the Republic of Uzbekistan is shown. The goal of the work is to create a modified republican regulatory document that meets modern requirements and provides an increase in the energy efficiency of designed solar hot water installations by 30%. The analysis was conducted with domestic and foreign experience in the design, and construction and operation of solar hot water installations for various purposes was studied and summarized. The selection of advanced technical achievements and scientific research of different countries in the field of energy saving and efficient use of solar energy has been carried out. In the process of revising the regulatory document, outdated regulations were excluded; new regulatory requirements were included, taking into account the current level of scientific and technological achievements, design and construction practices, and regional features of the Republic of Uzbekistan. The article introduces and substantiates main changes made to the previously existing building codes and rules, developed on the basis of the analysis of generally accepted results of completed research, development and experimental work, the study and synthesis of domestic and foreign experience in designing, building and operating solar hot water installations for various purposes.

Causes of hot and cold water system failure

The paper presents causes of the failures of hot and cold water systems. Most often they occur in the case of installations built with metal pipes and result from the use of improper materials and the adoption of wrong solutions. Failures are caused by chemical and electrochemical corrosion resulting from design and manufacturing errors. Further on, the corrosion process is briefly described. The most common causes of corrosion of hot water installations are discussed and examples of them are presented. On the basis of observations it can be stated that despite the knowledge about corrosion of hot and cold water installations, some of the them are improperly designed and constructed and exhibit high failure rates. The summary discusses the most common errors for different installation solutions.