Hot Water Outlet Research Articles

A Hot Water Split-Flow Dual-Pressure Strategy to Improve System Performance for Organic Rankine Cycle

The organic Rankine cycle (ORC) is widely used to recover industrial waste heat. For an ORC system using industrial waste hot water as a heat source, a novel hot water split-flow dual-pressure organic Rankine cycle (SFD-ORC) system is developed to improve the performance of the ORC. The maximum net power output was selected to compare three ORC systems, including basic ORC (B-ORC), conventional dual-pressure ORC (CD-ORC) and SFD-ORC. A genetic algorithm (GA) was used to optimize the parameters to search the maximum net power output of ORCs. The maximum net output power was taken as the standard of performance evaluation. The results show that, under the same hot water inlet temperature condition, the optimal hot water outlet temperature of B-ORC is much higher than that of CD-ORC and SFD-ORC, which indicates that less thermal energy could be utilized to convert to power in B-ORC. The optimal hot water temperature at the outlet of evaporator 1 in SFD-ORC is higher than that in CD-ORC, which means SFD-ORC could make more efficient use of the high-grade thermal energy of hot water. The SFD-ORC could obtain the highest net output power under the optimal parameter conditions, followed by the CD-ORC system, while the B-ORC has the lowest net output power. Moreover, with the increase in the hot water inlet temperature, the advantage of SFD-ORC becomes increasingly obvious. When the hot water inlet temperature is 90 °C, the net output power of SFD-ORC at is 6.22% higher than that of CD-ORC. The net output power of SFD-ORC at 130 °C increases to 9.7% higher than that of CD-ORC. The SFD-ORC presents better system performance and has great engineering application potential.

Pressure drop and heat transfer performance of microchannel heat exchanger with different reentrant cavities

The shape of the reentrant cavities has a great effect on the pressure drop and heat transfer performance of microchannel heat exchanger (MHE). In present study, MHEs with three reentrant cavity, i.e. circular, trapezoidal, and rectangular, were designed and manufactured. The influence of the cavity shape on the pressure drop performance, heat transfer performance and comprehensive performance of the MHEs were investigated. The pressure drop and Darcy friction coefficients were largest for the rectangular reentrant cavities, indicating that it exhibited the best pressure drop performance. At the same flow rate, the MHE with circular reentrant cavities had the lowest hot water outlet temperature and the MHE with rectangular reentrant cavities had the highest temperature, whereas the results were the opposite for the cold water outlet temperature. The Nusselt number was largest for the circular reentrant cavities. This indicates that the MHE with circular reentrant cavities had the best heat performance. Finally, the comprehensive performance index η was put forward. And the result found that the MHE with circular reentrant cavities had the highest comprehensive performance.

Experimental study on effect of operating parameters on performance of serially cascaded wastewater source heat pump

In order to maximize the recovery of heat energy from shower greywater, improve the operation stability of the wastewater source heat pumps and reduce the complexity of the system, a serially cascaded wastewater source heat pumps (SCWSHP) with large temperature difference was proposed. In this paper, an experimental system for testing the heating performance of the SCWSHP was built. The heating performance of the SCWSHP was analyzed under various operating conditions. And the operating conditions of the SCWSHP were discussed in order to realize that the amount of hot water heated by the SCWSHP is greater than the amount of greywater recovered. The results showed that when the greywater inlet temperature and out temperature are 30 °C and 6 °C, respectively, the outlet temperature of hot water can be heated to 50 °C if tc,i is 15 °C. But the maximum outlet temperature of hot water can only reach 41 °C if tc,i is 9 °C in order to guarantee the operation demand of the system. For the lower tap water inlet temperature, the shower greywater inlet temperature must be increased in order that the hot water outlet temperature can reach 45 °C. If tc,i is 6 °C, the greywater inlet temperature should be improved to 35 °C. As long as the outlet temperature of hot water meets the operation requirements, the hot water flow rate should be increased as much as possible, but the flow rate of greywater should be consistent with that of hot water. The results can provide key references for design and operation of the SCWSHP system.

Pressure Drop and Heat Transfer Performance of Microchannel Heat Exchanger With Circular Reentrant Cavities and Ribs

Abstract The rib arrangement has an important influence on the pressure drop and heat transfer performance of a microchannel heat exchanger (MHE) with circular reentrant cavities and ribs. In this study, four kinds of MHEs with circular reentrant cavity and ribs were designed, namely, circular reentrant cavities (circular), circular reentrant cavities and single-sided ribs (circular—single), circular reentrant cavities and odd-symmetric ribs (circular—odd), and circular reentrant cavities and double symmetric ribs (circular—double). The effect of the rib arrangement on the pressure drop and heat transfer performance of MHEs was numerically investigated by ansysfluent 15.0. The experimental platform was then designed and built for the subsequent experimental verification. The results showed that the pressure drop between the inlet and outlet of the MHE with circular reentrant cavities and ribs increased as the inlet flow increased. At the same inlet flowrate, the pressure drop between the inlet and outlet of the MHEs was largest for the circular reentrant cavities and double symmetric ribs, followed by the circular reentrant cavities and odd-symmetric ribs, circular reentrant cavities and single-sided ribs, and the circular reentrant cavities. The presence of the rib structure increased the inlet and outlet pressure drop of the MHE. The MHE with circular reentrant cavities and double symmetric ribs had the largest inlet and outlet pressure drop, followed by that with circular reentrant cavities and odd-symmetric ribs, that with circular reentrant cavities and single-sided ribs, and that with circular reentrant cavities, indicating that the latter exhibited the best pressure drop performance. At the same inlet flowrate, the MHE with circular reentrant cavities had the highest hot water outlet temperature and the MHE with circular reentrant cavities and double symmetric ribs had the lowest temperature, whereas the results were the opposite for the cold-water outlet temperature. This indicates that the heat transfer performance was best for the MHE with circular reentrant cavities and double symmetric ribs, followed by that with circular reentrant cavities and odd-symmetric ribs and that with circular reentrant cavities and single-sided ribs.

Residential water heater cleaning and occurrence of Legionella in Flint, MI

After the Federal emergency in Flint, MI was declared in early 2016 in response to elevated lead-in-water and incidence of Legionnaires’ disease, concerns arose that contaminants in residential water heaters could continue to contribute to poor quality tap water. Here, a comprehensive field survey of residential water heaters (n = 30) and associated water quality was conducted and the subsequent effects of an aggressive manual water heater clean-out was determined, including draining the tank and removing sediments via brushing and flushing. Before cleaning, inorganics accumulated in the tank sediments did not serve as a source of metals measured at hot water outlets. After cleaning, hardness- (calcium, magnesium, silica) and corrosion-associated inorganics (lead, iron, copper, aluminum, zinc) decreased by 64% in samples from sediment cleanout drain valves. Culturable L. pneumophila was only detected in 1 home (3.3%) prior to cleaning and 2 homes (6.7%) after cleaning, thus quantitative polymerase chain reaction was used to quantify potential effects on unculturable strains despite the limitation of differentiating live and dead cells. After the cleaning protocol, Legionella spp. and L. pneumophila gene numbers decreased or remained non-detectable in 83% and 98% of samples, respectively. Homes with less than 0.4 mg/L influent free chlorine tended to have quantifiable Legionella spp. gene numbers in water entering the home and had elevated L. pneumophila and Legionella spp. gene numbers throughout the home plumbing. Also, Legionella spp. and L. pneumophila gene numbers were highest for water heaters set at or below ∼42 °C and significantly decreased >51 °C, consistent with Legionella’s preferred temperature range. Examination of the only home that had culturable L. pneumophila both before and after the cleaning protocol revealed that the organism was culturable from several sample locations throughout the home, including in water representative of the water main. Notably, the home was located in close proximity to McLaren Hospital, where an outbreak of Legionnaires disease was reported, and the water heater had a setpoint within the Legionella growth range of 44.2 °C. Considering that other factors were more strongly associated with Legionella occurrence and water heater sediment was not detectably mobilizing to tap water, it was concluded that water heater cleaning had some benefits, but was not an overarching factor contributing to possible human health risks.

Hardware in the loop experimental study for the combined cooling, heat and power system controller

ABSTRACT Distributed power supply system has the advantages of energy saving, environmental protection, high reliability, high stability and so on. The combined cooling, heat and power (CCHP) system based on gas turbine is a distributed energy supply system which adopts the strategy of power cascade utilization. It can provide electric power, air conditioning chilled water and domestic hot water at the same time. In this paper, the construction scheme of the CCHP system based on gas turbine is proposed firstly. Afterward, a comprehensive dynamic model of the CCHP system based on gas turbine is established. The model consists of four mutually coupled sub-models. Then, the controller of the CCHP system is designed. In the operation mode of “electricity determines cold and heat“, three sets of PI algorithm with feedforward compensation are adopted to ensure the stability of combustion engine speed, temperature of chilled water outlet and domestic hot water outlet. Finally, a HIL simulation test of the CCHP system based on gas turbine is carried out. The test results show that the speed overshoot does not exceed 0.5% when the gas turbine is unloaded. The temperature of chilled water outlet of bromine cooler can achieve stable control. The temperature of domestic hot water outlet has a small overshoot and no steady state error. Therefore, the correctness of the control algorithm, the feasibility and effectiveness of the controller are verified.

Feasibility Analysis and Performance Evaluation and Optimization of a DXSAHP Water Heater Based on the Thermal Capacity of the System: A Case Study

The present work conducts an evaluation of the feasibility and the overall performance and consequent optimization of a direct expansion solar assisted heat pump (DXSAHP) employed for domestic water heating. For the study conducted R134a, R404A, R407C and R410A working fluids were evaluated as well as the use of four, six and eight flat-plate solar collectors and a worktime ranging from 1 to 6 h. The case study is based in Mexico City with a 300 L container and a hot water outlet temperature of 51 °C. The paper introduces a new evaluation criterion based on the thermal capacity and all the evaluations conducted throughout this research revolve around this performance metric. The results show that, the system would require at least 4 h of operation to achieve the outlet temperature. Additionally, it was found that the R410A refrigerant has the best heat transfer properties; with an average condensation heat rate of 6.31 kW, followed by the R407C with 5.72 kW, the R404A with 5.42 kW and the R134a with 5.18 kW. Diversely, the R134a refrigerant requires 0.402 kW of compression work, 62% less than the R410A, which requires 1.06 kW. Consequently, R134a delivers the highest COP, which ranges from 7 to 14, followed by the R407C and R404A refrigerants, which present a similar behaviour between them, with COP ranging from 5 to 9 and 4 to 8, respectively, and finally the R410A, achieving the lowest COP, ranging from 3.5 to 6.5. Moreover, it was found that the R134a presents a higher dispersion regarding the energy exchange rate, which reveals that it is the fluid most susceptible to external factors, such as the weather. Contrarily, the remaining refrigerants present a more consistent performance. Finally, the optimization revealed that the R407C refrigerant is the most suitable given that it requires 20% less compression work than the R404A. This provides the heat pump system with a steadier behaviour, a COP ranging from 7 to 8, 30% higher than R410A, a worktime decrease of 1.5 h and heat transfer area of 5.5 flat-plate solar collectors, equivalent to a 31% reduction, both compared to R134a.

Analysis and comparison of influence factors of hot water temperature in transcritical CO2 heat pump water heater: An experimental study

In order to investigate the factors that affect the hot water outlet temperature on air-source transcritical CO2 heat pump water heater, an experimental research is designed where the expansion valve opening is controlled to adjust the discharge pressure. The experiments are conducted at different compressor speeds, water-inlet flowrates and water-inlet temperatures. Then, a new indicator named unit temperature-lift cost (UTC) is proposed to evaluate the lifting effects of hot water temperature. The results show that the rise of hot water temperature leads to the decrease of the maximum coefficient of performance (COP) but the increase in both the gas-cooler outlet temperature at the optimal status and the optimal discharge pressure, which are mainly caused by the variations of gas-cooler outlet status. At ranges of compressor speeds, water-inlet flowrates and water-inlet temperatures, the UTCs always show a drop with a higher required hot water temperature, and the corresponding average UTCs are 0.054 °C−1, 0.042 °C−1 and 0.099 °C−1, respectively. According to the results, the method of controlling the water inlet flowrate should be taken as a priority to lift the hot water temperature of the system. The compressor speed is suitable to meet the needs of increasing hot water temperature and heating capacity simultaneously. It is not advisable to increase the hot water temperature by adjusting the water inlet temperature.

A study on the design and analysis of a gas engine heat pump water heater using shower wastewater as heat source

Abstract Shower wastewater contains large amounts of heat, and recovering and utilizing shower wastewater heat energy to heat shower water is of great significance for energy saving. This paper proposed a gas engine heat pump water heater (GEHPWH) using shower wastewater as the heat source. Thermodynamic models were built to evaluate the performance of the GEHPWH and compare it with an electrical heat pump water heater (EHPWH). The results show that the GEHPWH has higher hot water outlet temperature and coefficient of performance (COP) than the EHPWH under the same conditions. Furthermore, the GEHPWH can maintain stable hot water outlet temperature and higher primary energy ratio (PER) in variable water flow mode, which resolves the issue that the conventional EHPWH needs an auxiliary heat source. Finally, based on a case, the GEHPWH reveals smaller energy consumption and lower operating costs compared with three other conventional hot-water schemes.

Theoretical and practical analysis of waste heat recovery system in off-season rainbow trout production

The supply of heat for fish farms, especially during off-season production, is necessary for the establishment of commercial aquaculture. For this purpose, research was carried out on the supply of heating ener to a rainbow trout farm (cold water fish) using a waste heat recovery system in the city of Meshgin in Ardabil province. The study area has 20 indoor pools and 14 unguarded pools. The 14 pools that are in the indoor area, are used for this study. Seven pools of these 14 pools were at high altitude and other 7 pools were at low altitude. After collection of the temperature data for waste water ponds that had provided optimum temperature conditions in the off-season using geothermal fluid, three modes for waste heat recovery were designed according to the thermal, flow and physicochemical properties of the waste pond. In the first mode, the output of the first seven pools and the second seven pools were combined and the fluid flow rate reached to 24.92 L/sec. In the second mode, the output of the second seven pools (8.15 L/sec) was used to recover heat, and in the third case, the output of the first seven pools (at high-altitude pools and with the flow rate of 16.77 L/sec) was used to recover heat. After obtaining technical approval and determining the economic value of each component of the waste heat recovery circuit from specialized companies in Iran, the proposed systems were analyzed theoretically with COMSOL software. Because there was no equal rate of flow, velocity or geometry for comparison between the optimum state in the theoretical conditions of practice, the temperature differences between the input hot water and output cold water were used for all three modes of heat recovery. Technically, the results indicate that the second mode is best in both the theoretical and practical modes of the waste heat recovery circuit. The first mode recovery system had the smallest temperature difference between the hot water inlet and cold water outlet. Economically, the minimum cost of establishing a heat recovery system was for the second mode, with a decrease of 60.65% and 38.83% compared to the third and first modes, respectively. Considering technical and economic factors, the waste heat recovery system of the second mode was the most appropriate choice for the trout farm, both theoretically and practically. The first and third modes ranked next, respectively.

Solar absorption chiller performance prediction based on the selection of principal component analysis

In this paper, a method to predict the performance of an absorption chiller using solar thermal collectors as the energy input is analyzed rigorously. Artificial Neural Network (ANN) is developed based on experimental data to predict the performance of the solar absorption chiller system at Universitas Indonesia. In order to perform ANN accurately, some parameters such as chilled water inlet and outlet temperatures, cooling water inlet and outlet temperatures, solar hot water inlet and outlet temperatures, hot water inlet and outlet temperatures, ambient temperature and fuel consumption flow rate are chosen as the input variables. In addition, a Principle Component Analysis (PCA) is used to reduce the number of input variables for performance prediction. Without sacrificing the ANN's prediction accuracy, PCA identified the sensitive variables from all input variables. The developed ANN model combined with PCA (ANN + PCA) shows good performance which has a comparable error with ANN model, specifically the configuration 9–6-2 (9 neurons, 6 inputs, 2 outputs) of the ANN + PCA model leads to a COP root-mean-square error of 0.0145.

Clusters of Legionnaires' disease in period hotels with complex water systems: lessons learnt in the West Midlands, UK

BackgroundIn 2017 there were two distinct clusters of local travel-associated Legionnaires' disease associated with period hotels built in the 17th and 18th centuries in the West Midlands, UK. Both hotels had undergone frequent structural modifications. Five cases occurred 3 months to 2 years apart. The aim of this report is to share the learning from the investigations and challenges faced in achieving control of Legionella pneumophila in the water systems of dated buildings. MethodsEpidemiological information was obtained through structured cases interviews and through linked cases by the national surveillance scheme database. Hotel water system maintenance records were reviewed, and samples were taken at numerous timepoints and different locations, with an initial focus on facilities and rooms used by the cases. Sputum and environmental samples were tested in the reference laboratory and sequence-based typing was undertaken. FindingsUnsatisfactory levels of L pneumophila serogroup 1 were detected from hot and cold water outlets in both hotels. At one of the hotels L pneumophila serogroup 1, sequence type ST62 subtypes in clinical and environmental samples were indistinguishable. Both hotels were closed for business for months to undertake extensive remediation work. This closure was temporarily effective in achieving adequate control of legionella but 6 months later routine monitoring detected unsatisfactory levels. Achieving sustained legionella control in dated water systems and verifying safe endpoints for hotel re-opening has proven challenging for the regulatory bodies. InterpretationSustaining legionella control in the dated water systems of period buildings was demanding, and public confidence in the effectiveness of control measures was compromised. There were four key challenges: defining a cluster and the timely confirmation of when an outbreak has developed; using the cluster and outbreak definitions to inform the risk assessments and review of control measures in the environmental investigations; communicating the risk to the public and the media through clear messages; and seeking assurance on safety of water management systems in defining the endpoint for a cluster or outbreak investigation. FundingNone.

A numerical and experimental investigation for a triangular storage collector

In this study, an experimental and numerical investigation was conducted for a new solar collector design suitable for domestic utilization. The study was carried out to evaluate the performance of triangular collectors that were fabricated by cutting a cubic tank at different cutting planes.Experiments were done at different conditions including during summer and winter with and without the removal of hot water outlet. A systematic investigation on the hourly performance parameters of the system was conducted in all test conditions, which included mean storage temperature, velocity distribution, total stored energy and the best location for inlet and outlet water flows. The results revealed that the triangular collector day-long collection efficiency under no load condition was found to be 48.7% during winter with 40.5 °C maximum mean storage temperature and 65 °C maximum temperature for the hot water from the collector tip. During summer, the day-long collection efficiency was found to be 62.2% with 57 °C maximum mean storage temperature and 70 °C maximum temperature for the hot water from the collector tip. At continuous loading of the triangular collector, the collection efficiency was 55.7% during winter and 65.1% during summer. At continuous loading condition test, the maximum temperature difference between the collector outlet and inlet water was found to be 12 °C at 2 PM and 9 °C at the end of the winter day.To verify the experimental test results, a numerical study was conducted using Fluent software. The numerical results showed a good agreement with the experimental data obtained from this study.

Automatic testing system to evaluate the energy efficiency of electric storage water heaters

Background: The energy efficiency of electric storage water heaters is a concern for enterprises and customers because it is beneficial for energy saving. To decrease the workload of testing personnel and improve the testing efficiency, an automatic testing system for evaluating the energy efficiency performance of electric storage water heaters has been designed. Methods: The complete testing system includes a water supply subsystem, hot water outlet subsystem, hardware subsystem, and software subsystem. An application program was developed using Visual Basic to acquire the sensor data and transmit it in real time to a database server. The energy efficiency evaluating process was controlled by the application software,by combining the data acquisition technology, communication technology, and program logical control technology. Results: The designed system can run automatically and achieve reliable tests, two important parameters including the standing loss per 24 h and the hot water withdrawal rate were obtained. Conclusion: This system can be applied to evaluate the energy efficiency grades of electric storage water heaters.

Experimental investigation on the performance of transcritical CO2 ejector–expansion heat pump water heater system

The effects of hot-water outlet temperature, compressor discharge pressure, compressor rotation speed, and expansion valve opening on the ejector and overall system performance were investigated for tap water outlet temperatures ranging from 50 to 90 °C. The coefficient of performance (COP) of the ejector–expansion heat pump system reaches 4.6 when the tap water outlet temperature is 70 °C, which is 10.3% higher than the corresponding basic cycle. Compared to the basic system, adding an ejector is more effective for the generation of high-temperature hot water. The COP of the ejector–expansion heat pump system increases; however, the COP improvement ratio ΔCOP decreases with the increase in the discharge pressure because of lower pressure lift ratio and ejector efficiency. The COP and ΔCOP increase when the compressor rotation speed decreases under our test conditions; simultaneously, the heat capacity decreases.

Performance of absorption chillers in field tests

Absorption chillers can use waste heat, solar heat, or excess heat by cogeneration facilities to supply chilled water. Therefore, absorption chillers are important components for poly-generation, which can improve plant utilization and efficiency of the overall energy supply system.Currently, 27 new small and medium-scale (30–160 kW cooling capacity) absorption chillers with high efficiency in full- and part-load as well as low specific size and weight are the focus of two research projects sponsored by German Federal Ministries. The chillers are located in 20 different sites, four of them in Jordan and the rest in Germany. The main objective of these projects is to enhance trigeneration and solar cooling system efficiency.The Jordan projects and more than 70% of the German installations use dry cooling towers. Combined heat and power (CHP) plants or district heating grids provide the driving heat for regeneration at the German installations. Solar thermal collectors drive one German and all Jordan installations.Within the projects, the chillers are provided with an intelligent control algorithm that allows achieving several objectives at the same time. One of the objectives, of course, is to match the desired chilled water temperature as well as the cooling capacity. Another objective is, for instance, to fit the hot water outlet temperature. This is commonly essential in cogeneration to avoid emergency shutdowns of the CHP engine. The field operation shows that the deviation of said temperatures from the set point is usually less than ±0.5 K in operation. In those operational hours in which the temperatures of the heat source or heat sink do not allow to reach all objectives, a set of hierarchical aims can be established within the algorithm so that the chiller can be controlled to match its prioritized objectives.Furthermore, the designed absorption chiller performs dynamically and autonomously in a very large range of temperatures and flow rates. These can vary from 20% up to 150% of nominal conditions. This flexibility can be used to achieve up to 80% savings of electrical power consumption using speed-controlled pumps in part load conditions.In contrast to the common opinion that small and medium-scale absorption chillers are not competitive as compared to compression chillers, this paper shows applications in which absorption chillers are advantageous because of synergies with and multiple benefits within the rest of the energy supply system.

ORC cogeneration systems in waste-heat recovery applications

The performance of organic Rankine cycle (ORC) systems operating in combined heat and power (CHP) mode is investigated. The ORC-CHP systems recover heat from selected industrial waste-heat fluid streams with temperatures in the range 150 °C – 330 °C. An electrical power output is provided by the expanding working fluid in the ORC turbine, while a thermal output is provided by the cooling water exiting the ORC condenser and also by a second heat-exchanger that recovers additional thermal energy from the heat-source stream downstream of the evaporator. The electrical and thermal energy outputs emerge as competing objectives, with the latter favoured at higher hot-water outlet temperatures and vice versa. Pentane, hexane and R245fa result in ORC-CHP systems with the highest exergy efficiencies over the range of waste-heat temperatures considered in this work. When maximizing the exergy efficiency, the second heat-exchanger is effective (and advantageous) only in cases with lower heat-source temperatures (< 250 °C) and high heat-delivery/demand temperatures (> 60 °C) giving a fuel energy savings ratio (FESR) of over 40%. When maximizing the FESR, this heat exchanger is essential to the system, satisfying 100% of the heat demand in all cases, achieving FESRs between 46% and 86%.

Experimental investigation of a gas engine-driven heat pump system for cooling and heating operation

The present work aimed at evaluating the performance of a gas engine driven heat pump (GEHP) for cooling and hot water supply. A test prototype working with R134a was built, and the cooling performance with hot water supply were experimented in a range of evaporator water inlet temperature from 12 °C to 22 °C, ambient air temperature from 24.2 °C to 37 °C, and gas engine speeds from 1400 rpm to 2000 rpm. The results show that the effects of evaporator water inlet temperature and gas engine speed on the system performance are more significant than those of ambient air temperature. Average hot water outlet temperatures between 40.7 °C and 61.7 °C are obtained over the considered range of the external operating parameters and this met the temperature demand of domestic water for shaving, residential dish washing, and laundry. Moreover, the primary energy ratio (PER2) of GEHP system is between 1.14 and 1.45 with waste heat recovery.

Performance of working-fluid mixtures in ORC-CHP systems for different heat-demand segments and heat-recovery temperature levels

In this paper, we investigate the adoption of working-fluid mixtures in ORC systems operating in combined heat and power (CHP) mode, with a power output provided by the expanding working fluid in the ORC turbine and a thermal energy output provided by the cooling water exiting (as a hot-water supply) the ORC condenser. We present a methodology for selecting optimal working-fluids in ORC systems with optimal CHP heat-to-electricity ratio and heat-supply temperature settings to match the seasonal variation in heat demand (temperature and intermittency of the load) of different end-users. A number of representative industrial waste-heat sources are considered by varying the ORC heat-source temperature over the range 150–330°C. It is found that, a higher hot-water outlet temperature increases the exergy of the heat-sink stream but decreases the power output of the expander. Conversely, a low outlet temperature (~30°C) allows for a high power-output, but a low cooling-stream exergy and hence a low potential to heat buildings or to cover other industrial thermal-energy demands. The results demonstrate that the optimal ORC shaft-power outputs vary considerably, from 9MW up to 26MW, while up to 10MW of heating exergy is provided, with fuel savings in excess of 10%. It also emerges that single-component working fluids such as n-pentane appear to be optimal for fulfilling low-temperature heat demands, while working-fluid mixtures become optimal at higher heat-demand temperatures. In particular, the working-fluid mixture of 70% n-octane+30% n-pentane results in an ORC-CHP system with the highest ORC exergy efficiency of 63% when utilizing 330°C waste heat and delivering 90°C hot water. The results of this research indicate that, when optimizing the global performance of ORC-CHP systems fed by industrial waste-heat sources, the temperature and load pattern of the cogenerated heat demand are crucial factors affecting the selection of the working fluid.

The geothermal model of Mersin (Turkey) region

The purpose of the study is to present the geothermal model of Mersin (Camili) region geothermal area with its geology, hydrogeology, hydrogeochemistry and isotope hydrology. The 1/25000 scale geology map obtained from the literature research is revised. In order to obtain a geothermal model, geological crosssections are extracted in certain points on the revised geology map. There are 3 hot water outlets. There are MC-1, C-1 and Uclu Cesme deep drillings. MC-1 well is 420 m, approximately 43.6°C temperature and 35 L/s flow rate and C-1 is 150 m, 40.3°C and 35 L/s. There is no exact information about the depth of Uclu Cesme well, but its average temperature is 37.5°C and it has a very low flow rate. Isotope analyses of the water samples obtained from these three wells and the Icme Dere are carried out by using the IRMS method with δ18O–δ2H (Deuterium) and IAEA method with 3H (Tritium). Radioactive Alpha-Beta determination and Physico-chemical and Bacteriological analyses of MC-1 well are made by using EPA 900.00. δ18O–δ2H isotope ratios clearly indicate a meteoric origin for the waters. In the light of all this information, the revised 1/25000 scare geology map of Mersin Guneyyolu (Camili) geothermal area is obtained; it is found out that hot waters are of meteoric origin; and the isotope hydrology and hydro-chemical assessment of the area is conducted to shape the geothermal model.