Drain Water Heat Recovery Units Research Articles

Looking beyond energy efficiency targets: Life cycle sustainability of mechanical and water heating equipment in Canadian homes

The building sector's impacts on climate are widely acknowledged, leading to policies and standards promoting energy-efficient buildings. In order to achieve sustainability in a holistic sense, the environmental, social, and economic impacts of equipment used in buildings need to be evaluated. In this regard, a novel decision support framework is introduced to evaluate the heating and cooling equipment in single-family detached homes. Energy simulation, life cycle environmental, social, and economic analyses, and a multi-criteria decision-making method are used to identify the most sustainable set of equipment. This framework is demonstrated through its application on mechanical and water heating equipment in three existing residential buildings of varying energy efficiencies (low, medium, and high, the latter being net-zero home) over a 50-year study period.The results indicate that the carbon footprint of a natural gas furnace is six times higher than that of other equipment. In contrast, the drain water heat recovery unit showed the lowest impacts attributed to lower material and energy usage. For most equipment, the product stage accounted for more than 50% of the total impacts. When grouped, the equipment in the low-efficiency home showed the highest environmental impacts, while the equipment in the medium-efficiency home had higher social and economic impacts. Overall, the equipment set in a net-zero home is the best choice under equal, pro-social, and pro-economic scenarios and only lags behind the equipment set in a medium-efficiency home for pro-environmental scenario. The work will help improve sustainable building policies beyond immediate energy and operational cost savings.

Thermal effectiveness and NTU of horizontal plate drain water heat recovery unit - experimental study

The operating characteristics of plate heat exchanger in horizontal drain water heat recovery unit for domestic shower system were investigated in an experimental study. Based on test data the thermal effectiveness (ε) and number of heat transfer units (NTU) were calculated. The tests were carried out in simulated real-world conditions in three shower water flow rates (water consumption levels) for 4, 8 and 12 l/min, and two primary and secondary flows configurations (balanced and unbalanced), as a reflection of the three shower intensity standards and water temperature range of 30–50 °C covering the usual user-specific shower conditions. The least favorable test results (ε = 18.6% and NTU = 0.24) were obtained for the drain water temperature of 26.6 °C and cold water / drain flow rate at 12/12 l/min. The most beneficial results (ε = 50.0% and NTU = 0.99) were obtained for the sewage temperature of 50.8 °C and 4/12 l/min. It has been shown that the higher the flow on the drain water side and lower on the cold water side, the better the effectiveness. For a system with equal and low flows on both sides, the drain temperature change has a negligible effect on the effectiveness (4% growth with a drain temperature increase of 25.4 °C for 4/4 l/min). The paper presents developed easy-to-use charts of the variability of the effectiveness and NTU with the drain water temperature relates to a different set of primary and secondary flows in horizontal, plate, compact drain water heat recovery exchanger. The results of effectiveness obtained in the research were compared to the values presented in the literature for other drain water heat recovery units, both in vertical and horizontal applications.

Experimental Development of the Horizontal Drain Water Heat Recovery Unit

The increase in energy demand, the scarcity of resources, as well as the adverse environmental impact of burning fossil fuels make it necessary to diversify the energy sources used. This also applies to the residential sector, which accounts for a significant proportion of global energy consumption. Particular attention should be paid to water heating, as the importance of this process in the energy balance of buildings is steadily increasing. One of the methods used to decrease energy consumption for heating water is to recover heat from greywater. However, commercially available horizontal drain water heat recovery (DWHR) units are characterized by low effectiveness, which creates a need for further research to improve it. The aim of the paper was to evaluate the possibility of improving the effectiveness of a circular horizontal DWHR unit through the use of baffles. Six different baffle models for installation in the greywater section of the heat exchanger were analyzed. The tests were conducted under the assumption of the installation of the DWHR unit on the horizontal shower waste pipe. They showed that the effectiveness of the unit equipped with baffles was higher by several to as much as 40% compared to the DWHR unit without baffles. This is tantamount to an increase in annual financial savings resulting from greywater heat recovery, as well as a reduction in CO2 emissions into the atmosphere. However, it was not possible to clearly identify the optimum baffle model. In any case, the selection should consider the hydraulic conditions in the heat exchanger before installing the baffles. The results can provide guidance for companies interested in bringing new equipment and technologies to the market.

Horizontal Shower Heat Exchanger as an Effective Domestic Hot Water Heating Alternative

Wastewater has significant potential as a source of clean energy. This energy can be used both within external sewer networks and on the scale of individual residential buildings, and the use of shower heat exchangers appears to be the most reasonable solution. However, in the case of Poland, the problem is still the unwillingness of society to use this type of solution, caused mainly by the lack of space for the installation of vertical drain water heat recovery (DWHR) units and the low efficiency of horizontal units. In response to this issue, the efficiency of a new compact shower heat exchanger designed to be mounted below the shower tray, as well as its linear counterpart, was investigated under various operating conditions. In addition, the financial efficiency of using the compact DWHR unit with average water consumption for showering was evaluated. For this purpose, discount methods were used to estimate the financial efficiency of investments. The study showed that the compact shower heat exchanger has higher efficiency than its linear counterpart. Depending on the temperature of cold water and the flow rate of both media through the heat exchanger, it achieves efficiencies ranging from 22.43% to 31.82%, while the efficiency of the linear DWHR unit did not exceed 23.03% in the study. The financial analysis showed that its use is particularly beneficial when the building uses an electric hot water heater. The investment’s sensitivity to changes in the independent variables is small in this case, even with low water consumption per shower. The only exceptions are investment outlays. Therefore, the compact DWHR unit is a clean energy device, which in many cases is financially viable.

Financial Analysis of the Use of Two Horizontal Drain Water Heat Recovery Units

The growing interest in the use of unconventional energy sources is a stimulus for the development of dedicated devices and technologies. Drain water heat recovery (DWHR) units can be an example of such devices. They allow the recovery of part of the heat energy deposited in grey water. This paper describes the results of research on the assessment of the financial profitability of the use of two horizontal heat exchanger solutions, taking into account the actual distribution of cold water temperature during the operating year in the plumbing and two operating regimes of the premises as the residential and service facilities. The analysis showed that the use of a horizontal heat exchanger with increased efficiency in a dwelling in a 15-year life cycle allowed for achieving more than twice as much savings (reaching up to EUR 1427) compared to a classic horizontal heat exchanger. At the same time, it was shown that the installation of this type of equipment was more profitable the greater the water consumption of the premises. The article also notes the impact of cold water temperature in the installation on the results of the analysis. It was featured that taking temperature on the basis of installation design recommendations led to significant distortions in the financial analysis. On the other hand, comparing the method of averaging the cold water temperature (daily, monthly and yearly), it was determined that averaging the temperature over the annual cycle was an acceptable simplification of the model. The research results presented in the paper have a practical aspect and may constitute guidelines for designers and potential investors. In addition, they can be an incentive to continue research on heat exchangers by other scientific centers, which on a global scale will increase the universality of their use.

Drain water heat recovery horizontal for energy conservation and reduction of CO2 emissions

One of methods to reduce energy consumption for hot water heating is install of Drain Water Heat Recovery (DWHR) units. The purpose of using this device is to take the thermal energy of the warm drainage water and transfer it to incoming cold water. Many DWHR systems work optimally in a vertical position. Due to the waste water flow in drain pipes. But these requirements are prohibitive to be applied on a large scale of this technology, as many buildings do not have enough space to accommodate the vertical DWHR in their sewage drainage system. This paper presents testing and analysis of the horizontal DWHR system. The result of the test showed the level of effectiveness of the horizontal DWHR unit created by 25.54 percent. Implementation of this technology in regional area, is one of the potential opportunities for energy saving, and reduce CO2 gas emissions.

An Analysis of Eco-Technology Allowing Water and Energy Saving in an Environmentally Friendly House—A Case Study from Poland

The Life Cycle Cost (LCC) analysis on selected alternative systems was carried out to reduce the demand for potable water and energy in a detached house designed in accordance with the concept of environmentally friendly house. The tests included a rainwater harvesting system, graywater recycling system, solar panels, photovoltaic panels, air heat pumps, ground heat pumps, wind turbines, drain water heat recovery units, and biomass boilers. The analysis was made for many investment variants where different combinations of the mentioned solutions were applied. In addition to the LCC analysis, some tests were also carried out to determine an impact of the investment options on the environment. This was done by calculating CO2, SO2, NOx, CO and dust emissions. The research was carried out for a different number of occupants and variable levels of water consumption, which allowed determining the impact of these parameters on the results obtained. They showed that for any of the computational cases the traditional option of the installation was not the most advantageous solution in financial and environmental terms, and the systems in question could be an alternative to this option. Thanks to their implementation, the consumption of fossil energy resources and natural water resources will be reduced, and the emission of pollutants will be limited, which will contribute to an improvement of the natural environment.

Opportunities and Threats of Implementing Drain Water Heat Recovery Units in Poland

In recent years an increase of interest in usage of renewable energy sources as a substitution of fossil fuels is being noticeable. However, the waste heat potential, which can be used as an additional source of energy for heating water in buildings, is being omitted. The sources of this heat can be grey water discharged from such sanitary facilities as showers or washing machines. In response to this issue, we took on the task to define and analyze key factors affecting the development of DWHR (Drain Water Heat Recovery) systems using PESTLE (political, economic, social, technological, legal and environmental) analysis. The strengths and weaknesses of these systems were also identified. The studies were based on CFD (computational fluid dynamics) modeling tools. In the Autodesk Simulation CFD software environment, a DWHR unit was made, which was then analyzed for heat exchange efficiency. The obtained results were the basis for preparing the strategy for the development of Drain Water Heat Recovery systems. It was made using the SWOT/TOWS (strengths, weaknesses, opportunities and threats/threats, opportunities, weaknesses and strengths) method, which precisely orders information and allows presenting the project characteristic in readable way for a recipient. The results of the conducted analysis indicated the lack of acceptance on the part of potential users and the resulting need to promote the use of Drain Water Heat Recovery systems at residential level.

Comparison of two-prototype near-horizontal Drain Water Heat Recovery units on the basis of effectiveness

Recovery of energy carried by greywater is possible, for instance, through application of Drain Water Heat Recovery (DWHR) units at the drain water outlet from a shower unit. This paper reports results of a study concerning assessment of rationale behind the use of two different horizontal DWHR units. The analysis, carried out in laboratory conditions proved that equipping of the unit with properly shaped baffles can significantly increase its effectiveness. The effect was observed for all flow rates and device body bottom slopes adopted for the analysis. The paper points out the effect of difference of temperatures between the preheated water and the greywater giving up the heat. The effect turned out to be small in case of the compared devices. Results presented in the paper are of a practical value and can be used as guidelines for designers and potential investors.

HOUSEHOLD DRAIN WATER HEAT RECOVERY UNIT

In this article the possibility of energy recuperation from waste water is considered. The example of numerical simulation drain water heat recovery unit in household is represented. It is obtained that household can recuperate some heat that usually consider as a loss.

Evaluating the financial efficiency of energy and water saving installations in passive house

The article contains the outcomes of the Life Cycle Cost analysis for alternative energy and water sources utilized in passive buildings. The solutions taken into account included: heat pumps, solar collectors, photovoltaic panels, Drain Water Heat Recovery units, Rain Water Harvesting Systems and Greywater Recycling Systems. In addition, air pollution emission reduction was also calculated for all the installation variants analyzed. The analysis have shown that the systems under consideration could serve as alternatives for traditional installations. Their use has resulted in reductions in the consumption of fossil fuels and natural water resources, thus contributing to environmental improvements.

IMPROVING THE ENERGY EFFICIENCY OF RESIDENTIAL BUILDINGS BY USING A DRAIN WATER HEAT RECOVERY SYSTEM

Continuously increasing energy prices, as well as the increasing number of legal stipulations, bring to the attention of scientists the necessity of finding solutions for energy saving by using different heat sources. According to the EU Action Plan, the highest potential of energy savings (27-30% until 2020) will be applied to the existing buildings. Under the circumstances of environmental issues, research on the use of secondary energy resources is of great interest, being a concern in the context of sustainable development. The aim of the present paper is to accumulate knowledge on how a drain water heat recovery unit using a heat pipe heat exchanger performs under different drain water flow profile scenarios. Researching how the intermittent behaviour of the drain water influences the performance for this type of system is important because it gives insight on how the system will perform in a real life situation. In this paper the authors investigated the performance of a heat recovery unit, from drain water heat recovery. Investigation of the heat recovery unit performance shows that the heat pipe has the capability to recover more than 30% of the available heat in the drain water, at the flow rates investigated (0.3 0.5 m3/hour). The application of the presented solution shows that a heat recovery system of this type has the possibility to recover a large portion of the available heat if it has been achieved in those buildings where the hot water consumption is higher (housing complexes, university campus, hotels, swimming pool, sport and leisure, hospital/healthcare, restaurants, laundry, pharmaceutical manufacturing).

Analysis of profitability of using a heat recovery system from grey water discharged from the shower (case study of Poland)

The paper analyses the profitability of the use of Drain Water Heat Recovery units. An original simulation model was used for this purpose, and a detached residential building located in Poland was selected as the test facility. The conducted analysis proved that the type of the hot water heater has decisive influence on the profitability level of such an investment. Application of the abovementioned technology is particularly profitable, when water is heated with the use of an electrical device. When the energy source in the system is a gas water heater, the obtained calculation results are not as favourable, and the period of investment return in many cases exceeds the expected service life of these devices. Moreover, the analysis demonstrated that the potential energy savings, and thus also the financial savings, may be in both cases increased as a result of simultaneous intake of water from various water taps.

Drain water heat recovery storage-type unit for residential housing

The drain water heat recovery (DWHR) system is an interesting household technology to reduce energy costs and environmental impact. The objective of the utilisation of these devices is the recovery of the waste heat from domestic warm drain water, and transferring it to cold water entering the house. A drain water heat recovery unit has been built in this work. The authors are using both numerical and experimental tools to design and study the performance of this device, focusing on the analysis of a specific drain water heat recovery storage-type based on a cylindrical tank with an internal coiled pipe. The numerical simulation has been performed using an in-house platform, where the different elements of the DWHR storage are linked to solve the system. On the other hand, an experimental infrastructure has been developed to analyse of the system, which has been instrumented to provide detailed information of its heat recovery and storage capacities and temperature map. Different internal flow rates and operational temperatures have been studied. From the results obtained it can be said that the device shows interesting heat recovery and storage capacities, while the numerical platform shows promising comparison results against the experiments.

Analysis of profitability of rainwater harvesting, gray water recycling and drain water heat recovery systems

Gray water recycling and economical use of rainwater can be a valuable alternative source of water, especially for non-potable uses. These sources are seen as the basis of change in waters management, which gives a possibility of protection of still shrinking water resources. Taking into account continuing urbanization and population growth in the world, not only the management of water resources requires a change in attitudes, but also the management and conservation of conventional fuels that energy is generated of, and that are required for the development and functioning of urban areas. Bearing this in mind, some studies have been performed in order to establish the cost-effectiveness of application systems capable of reducing the demand for tap water and electricity used to heat it. A financial analysis with an application of the Life Cycle Cost methodology has been conducted for a multi-family residential building for seven different variants of installation of water and sewage, which assumed the use of the following solutions: gray water harvesting system, rainwater harvesting system and drain water heat recovery units. This analysis showed that the use of these systems in the tested building is financially viable, despite the fact that their implementation is associated with incurring higher investment cost than in the base case (Variant 0). The study was expanded by a sensitivity analysis on the basis of which it was possible to conclude that the project involving the use of alternative sources of pending water and energy in this building is only slightly susceptible to changes in calculation parameters.

Performance of two domestic solar water heaters with drain water heat recovery units: Simulation and experimental investigation

This paper presents an investigation on the performances of drain water heat recovery (DWHR) system and two solar domestic water heaters (SDWH). The DWHR units and water heater systems were recently installed side-by-side at the Archetype Sustainable Twin Houses at Kortright Center, Vaughan, Ontario. The first SDWH system in House A consists of a flat plate solar thermal collector in conjunction with a gas boiler and a DWHR unit. The second SDHW system in House B consists of an evacuated tube solar collector, an electric tank, and a DWHR unit. The extrapolated results based on the experimental study showed that the DWHR unit is capable of an annual heat recovery of 789 kWh and an overall effectiveness of about 50%. The flat plate and evacuated tubes collectors based SDWH systems produce an annual thermal energy output of 2038 kWh and 1383 kWh, respectively.

Simulation and experimental investigation of two hybrid solar domestic water heaters with drain water heat recovery

In this paper, the performance of two solar domestic hot waters (SDHW) with drain water heat recovery (DWHR) units is investigated. Both SDHW systems are recently installed at the Archetype Sustainable Twin Houses at Kortright Center, Vaughan, Ontario. The first SDWH system in House A consists of a flat plate solar thermal collector in combination with a gas boiler and a DWHR unit. The second SDHW system in House B includes an evacuated tube solar collector, an electric tank, and a DWHR unit. Both systems are modeled in TRNSYS, and the models are validated by experimental data. The addition of the DWHR and the flat-plate solar thermal collector would result in 1831 kWh of annual energy saving in House A. While the addition of the DWHR and the evacuated tube collector in House B would result in an annual energy saving of 1771 kWh. Subsequently, the models are used to investigate the performance of similar systems for five major Canadian cities of Halifax, Montreal, Toronto, Edmonton, and Vancouver. The conjunctions of solar thermal collectors with DWHR units are found most beneficial in Edmonton. It is also noted from experimental and simulated results that flat-plate solar collector-based water heater produced more thermal energy than the system based on the evacuated tube solar collector for all major Canadian cities. Copyright © 2015 John Wiley & Sons, Ltd.

Financial analysis of the implementation of a Drain Water Heat Recovery unit in residential housing

One of the ways of diminishing energy consumption for hot water heating is the use of Drain Water Heat Recovery (DWHR) units. The aim of the use of these devices is thermal energy recovery from warm drain water and transferring it to incoming cold water. This paper presents the calculation model that allows the estimation of the financial efficiency of the project involving the construction of a shower Drain Water Heat Recovery system in a single-family dwelling house. The presented method of investment risk assessment can be used for decision making by individual users, designers and others. The study of the financial performance was carried out for the various parameters of the installation and the different heat recovery system configurations. From investors point of view the most beneficial option of heat recovery system installation is the system in which preheated water is fed to both the hot water heater and shower mixing valve. Additionally, it was proved that obtained financial results are affected by showering time and water consumption. DWHR units will be therefore particularly beneficial to apply in case of swimming pools, sports facilities or fitness clubs, where high rotation of users is observed.