Cooling Water Inlet Temperature Research Articles

Efficiency enhancement of photovoltaic-thermoelectric generator hybrid module by heat dissipating technique

Exploring substantial solar irradiation and recuperating excess heat generated during photovoltaic energy conversion is a critical issue. The efficiency of photovoltaic systems (PV) is significantly depend on the increased operating temperatures encountered by solar radiation. One conceivable option for improving the conversion of solar energy is to integrate a photovoltaic (PV) panel with a thermal-electric generator (TEG) material module to create a hybrid system. This study proposed a parallel PV-TEG hybrid module that effectively harvests the maximum solar energy spectrum while maximizing the use of heat generated by the thermoelectric material to improve the overall system efficiency. The proposed module consists of a photovoltaic unit, thermoelectric material module and passive cooling of fluid channels. The aim of this work was to develop a PV-TEG hybrid system and create an energy simulation model in a MATLAB environment to analyze the model's performance under various operational conditions by applying both theoretical and experimental approaches. Findings showed considerable concurrence. At 13:00, when the PV surface temperature was 54 °C, the PV efficiency reached to its lowest value of 12.0 %. Nevertheless, the highest TEG efficiency recorded was 4.7 % at 12:00 h. The efficiency of the TEG module was significantly affected by weather conditions, inlet cooling water temperature, and fluid flow rate in comparison to both the PV efficiency and the thermal efficiency.

Thermal performance analysis and optimization of a heat pipe-based electronic thermal management system using experimental data-driven neuro-genetic technique

Heat pipes are highly efficient heat transfer devices and are used widely to dissipate heat generated by electronic components, thereby maintaining their operating temperatures and preventing overheating. The present study deals with the thermal performance prediction of a cylindrical heat pipe (length 380 mm) based electronic thermal management system using steady-state experimental investigation. The experiments are conducted under varying operational conditions, including heat inputs (10–50 W), condenser cooling water inlet temperatures (288.15, 293.15, and 298.15 K), and flow rates (10, 25, and 40 LPH). The study shows that the evaporator temperature of the heat pipe consistently rises with the increase in heat inputs for all tested conditions. The lowest evaporator temperature (311.42 K) is noticed for the cooling water inlet temperature of 288.15 K across all heat inputs. Notably, at 10 LPH, the heat pipe supplied with cooling water at 288.15 K exhibits reductions of up to 1.47 % and 2.29 % compared to 293.15 K and 298.15 K, respectively. Similar trends are also observed at 25 LPH and 40 LPH. The heat pipe’s thermal resistance is lowest (0.95 K/W) at a cooling water inlet temperature of 298.15 K. At 10 LPH, there are reductions of 10.19 % and 5.62 % compared to 288.15 K and 293.15 K, and at 40 LPH, reductions are 15.66 % and 7.89 %. The heat pipe’s evaporator heat transfer coefficient also plays a significant role and is maximum for the cooling water inlet temperature of 288.15 K at a flow rate of 10 LPH. To understand the complex behavior of the heat pipe and for better prediction of its thermal performance, a neuro-genetic (experimental data-driven artificial neural network and genetic algorithm) optimization technique is considered in the study. This predicts the optimal combination of operating parameters (heat input, cooling water inlet temperature, and flow rate) to minimize the heat pipe’s evaporator wall temperature which is found to be 312.54 K at a heat input of 10 W, flow rate of 10 LPH, and cooling water inlet temperature of 289.14 K. These input combinations are further validated through the experiments and the error in the heat pipe’s evaporator temperature is found to be 0.66 % only. Overall, this neuro-genetic technique underscores the importance of optimizing operational parameters for enhanced heat pipe performance and offers valuable insights for electronic cooling systems.

Comparative analysis of solar-powered heat pump systems for decarbonization of process heating and cooling applications: Case of milk pasteurization

The dairy processing industry is heavily dependent on fossil fuels for heating applications at different temperature levels and contributes to greenhouse gas (GHG) emissions. Besides, process cooling, product refrigeration, and storage are mainly reliant on vapour compression refrigeration technologies. This study investigates the performance of solar photovoltaic (PV) and solar thermal (ST) powered heat pumping technologies for simultaneous heating (at 75 °C) and cooling (at 2 °C) applications in a selected typical thermal process in a dairy processing plant (milk pasteurization). An ammonia/water absorption heat pump (AHP) and a two-stage R717 vapour compression heat pump with an open intercooler (VCHP) are used in the present study. The VCHP and AHP are powered by market-available solar PV modules and ST collector technologies. The electrical COP and exergy COP of the VCHP were about 4.710 and 0.535, respectively. The AHP operates at a thermal COP and exergy COP of 0.979 and 0.301 when the driving hot water and absorber cooling water inlet temperatures are 160 °C and 30 °C. The grid-connected PV-VCHP system and ST-AHP with natural gas-fired auxiliary heater operate at an annual solar fraction of 0.533 and 0.572, respectively, for a typical weather condition in Barcelona (Spain).

Operating characteristics of an adsorption chiller with heat and mass recovery scheme for low-grade heat source

Waste heat recovery from data center is regarded as one of the most promising application of adsorption refrigeration in the future. To better understanding of the system, the operating characteristics, including temperature, pressure and heat exchange capacity, of the adsorption chiller for such low-grade heat source should be revealed. Unfortunately, they have not been detailedly reported yet. In this paper, lab experiments on a silica gel-water adsorption chiller prototype with heat and mass recovery scheme are implemented. The results show that this chiller can achieve 3.17 kW of average cooling power and 0.482 of coefficient of performance under the conditions of 60 °C hot water inlet temperature, 30 °C cooling water inlet temperature and 22 °C chilled water inlet temperature. The temperature and pressure characteristics reveal that adsorbent bed desorption phase results in the worsening of the deviation from ideal cycle when compared to its adsorption phase. Hence, the heat and mass transfer performance of bed in desorption phase is prioritized to be enhanced. The analysis on heat exchange capacity indicates that mass recovery operation is more beneficial to the adsorption reaction. The optimal heat recovery time is found to be 24 s while the heat recovery efficiency is 0.711.

Integrating phase-change thermal storage into the indirect dry-cooling system of a thermal power unit and optimal operation strategy

Extreme conditions (high ambient temperature and crosswind speed) reduce the cooling efficiency of dry cooling towers, consequently impairing the thermal performance of thermal power units (TPUs). Phase-change material thermal storage equipment (PCMTSE) is integrated into an indirect dry-cooling system of the TPU to realize a partial cooling load of the cooling tower, thereby stabilizing and improving the thermal performance of the TPU. A model of the TPU and numerical model of the hybrid indirect dry-cooling system are established and coupled, with the inlet cooling water temperature of the condenser serving as the iterative criterion. Two integration schemes are proposed, one with the PCMTSE downstream (Scheme A) and the other with it upstream (Scheme B) of the dry cooling tower. The results show that Scheme A is recommended owing to its superior efficiency in terms of coal savings. The effects of the unit power load on the coal-savings efficiency of the PCMTSE during its charging and discharging processes have been revealed. Operating the PCMTSE at higher power loads aids in improving the thermal efficiency of the TPU during the PCMTSE charging and discharging processes. The charging process should be started at the “three high” working conditions: a high ambient temperature, crosswind speed, and unit power load. The working conditions that allow only one cooling water pump to operate should first be considered for the discharging process, and the “three high” working conditions should then be selected. The TPU equipped with the PCMTSE can save 11.42 tons and 12.74 tons of coal in two typical extreme daily conditions with the implementation of the proposed operating strategy.

Research on Off-Design Characteristics and Control of an Innovative S-CO2 Power Cycle Driven by the Flue Gas Waste Heat

Recently, supercritical CO2 (S-CO2) has been extensively applied for the recovery of waste heat from flue gas. Although various cycle configurations have been proposed, existing studies predominantly focus on the steady analysis and optimization of different S-CO2 structures under design conditions, and there is a noticeable deficiency in off-design research, especially for the innovative S-CO2 cycles. Thus, in this work aimed at the proposed novel S-CO2 power cycle, off-design characteristics and corresponding control strategies are investigated for the waste heat recovery. Based on the design parameters of the S-CO2 cycle, structural dimensions of printed circuit heat exchangers (PCHEs) and shell-and-tube heat exchangers are determined, and design values of turbines and compressors are specified. On this basis, off-design models for these key components are formulated. By manipulating variables such as cooling water inlet temperature, cooling water mass flow rate, flue gas inlet temperature and flue gas mass flow rate, cycle performances of the system are analyzed under off-design conditions. The simulation results show that when the inlet temperature and the mass flow rate of cooling water vary separately, the thermal efficiency both can reach the maximum value of 28.43% at the design point. For the changes in heat source parameters, the optimum point is slightly deviated from the design condition. Amidst the fluctuations in flue gas inlet temperature, the thermal efficiency optimizes to a peak of 28.56% at 530 °C. In the case of variation in the flue gas mass flow rate, the highest thermal efficiency 28.75% can be obtained. Furthermore, to maintain the efficient and stable operation of the S-CO2 power cycle, the corresponding control strategy of the cooling water mass flow rate is proposed for the cooling water inlet temperature variation. Generally, when the inlet temperature of cooling water increases from 23 °C to 27 °C, the cooling water mass flow should increase from 82.3% to 132.7% of the design value to keep the system running as much as possible at design conditions.

Study on the active cooling effect and convective heat transfer performance inside the rail

In order to study the impact of different influencing factors on the active cooling effect of electromagnetic rail. The effects of the flow velocity of cooling medium, the geometric shape of the cooling channel, the cooling water inlet temperature and the nanoparticle mass fraction on the cooling effect of rail are experimentally investigated. The results indicate that increasing the flow velocity of cooling medium can enhance the heat transfer effect. But when the flow velocity exceeds 2 m/s, further increasing the flow velocity has little effect on enhancing heat transfer, and the correlation between the Nusselt number and the Reynolds number has been obtained and expressed as Nu=0.316Pr1/3Re0.530. Among the three cooling channel geometries studied in this article, square channel has the best cooling effect. The inlet temperature of cooling water has little effect on the convective heat transfer coefficient, but has a significant impact on the thermal equilibrium temperature of the rail. The mass concentration of nanoparticles has a significant impact on the cooling effect of the rail. The larger the mass fraction of nanoparticles, the greater the convective heat transfer coefficient, and the lower the rail peak temperature after reaching thermal equilibrium. However, if the concentration of nanoparticles continues to increase, the effect of enhancing heat transfer will gradually weaken.

NUMERICAL AND EXPERIMENTAL INVESTIGATIONOF STEAM FILM CONDENSATION ON A VERTICAL TUBE

NUMERICAL AND EXPERIMENTAL INVESTIGATIONOF STEAM FILM CONDENSATION ON A VERTICAL TUBE

Research on geothermal-driven single-effect absorption refrigeration systems with different working fluids: energy and exergy analysis

Abstract Geothermal energy is not only environmentally friendly and has low carbon but also represents a nonintermittent technology. It is anticipated that its utilization in human society will experience rapid growth in the coming decades. Absorption refrigeration can be employed for the recovery of geothermal resources. However, the low performance of absorption refrigeration systems has hindered their development. In order to advance absorption refrigeration technology suitable for geothermal energy recovery, this study developed a mathematical model for an absorption refrigeration system using 55% lithium bromide (LiBr) and 35% lithium chloride (LiCl) solutions as working fluids. The impact of various parameters, including cooling water conditions, chilled water conditions, heat source parameters, and working fluid concentration, on the thermodynamic performance, system efficiency, and exergy efficiency of a single-effect absorption refrigeration system was analyzed. The results reveal that the cooling water inlet temperature and flow, chilled water inlet temperature, heat source inlet temperature, and working fluid concentration are the primary factors affecting the thermodynamic performance and exergy efficiency of the absorption refrigeration system. The coefficient of performance (COP) of the system increases with higher cooling water flow, chilled water inlet temperature, and working fluid concentration, but decreases with higher cooling water inlet temperature. Within a certain temperature range, the COP increases with higher heat source temperature. The effective COP (ECOP) increases with higher cooling water inlet temperature, cooling water flow, chilled water inlet temperature, and working fluid concentration, while it decreases with higher heat source temperature. The highest COP values for the LiBr and LiCl solution single-effect absorption refrigeration systems are 0.795 and 0.785, respectively, while the highest ECOP values are 0.694 and 0.684, respectively.

Microchannel cooling plates with non-uniform airfoil fin arrangement for large-capacity marine battery: An experimental study

In the process of charging and discharging, the heat generation of the battery is uneven, which is more obvious for large-capacity batteries. To maintain the performance of the battery, the thermal management system based on the cooling plate is of critical importance. In this paper, the non-uniform airfoil fins arrangement of microchannel cooling plates for marine large capacity battery thermal management are designed and tested. The cooling performances of the uniform airfoil fins arrangement (UAFA), non-uniform airfoil fins arrangement 1 (N-UAFA 1) and non-uniform airfoil fins arrangement 2 (N-UAFA 2) are experimentally investigated. The maximum temperature (Tmax) and temperature standard deviation (SD) of battery module during charge and discharge process are compared with the variation of the volume flow rate (qv), the cooling water inlet temperature (Tin) and the charge–discharge rate (CR). The experimental results demonstrate that increasing qv and decreasing Tin would contribute to lower Tmax but higher SD. Both Tmax and SD increase with the CR increasing. The cooling effectiveness of the non-uniform airfoil fins arrangement is validated by the reduced Tmax and the robustness in SD control. In particular, the newly designed N-UAFA 2 microchannel could relief the contradiction between cooling capacity and the temperature uniformity. For all the working conditions, the N-UAFA 2 exhibited the best performance. Especially at the CR of 0.5C, the N-UAFA 2 could manage the Tmax and the SD below 36.8 °C and 1.5 °C, respectively.

Experimental investigation of water vapor condensation from flue gas in different rows of a heat exchanger model

Condensing heat exchangers (HE) are used in many applications because of their usability with different fluids and a wide operating range in terms of pressure, temperature and power. Despite that, the thermal design of condensing heat exchangers is still not optimized, due to the complexity of the condensation process and lack of related research.This paper presents results of experimental investigations of biofuel flue gas water vapor condensation on vertical tubes in different rows of a tube bundle in a crossflow. The effects of water vapor mass fraction, inlet flue gas temperature and the Reynolds number on heat transfer when the inlet cooling water temperature and flow rate are constant were analyzed. The results obtained showed that the main parameters which had the most influence on the condensation process were the water vapor mass fraction in the flue gas and its temperature at the inlet to the test section. In the range of inlet flue gas Reynolds numbers investigated, the Re effect on heat transfer was not as significant as the effect of the parameters indicated above. However, the Re number had some influence on the heat transfer variation along the inline tube bundle. A comparison of the average Nu number in the case of dry air with the experimentally determined average Nu number, even with low condensable gas mass fraction (6 %), showed that it increased considerably. A correlation was proposed, which helps to determine the average Nu number for the heat exchanger in the range of experiments performed.

Development and experimental study of a compact silica gel-water adsorption chiller for waste heat driven cooling in data centers

In recent years, data centers have experienced rapid construction, leading to a significant surge in energy consumption, and cooling systems have emerged as prominent energy consumers of data centers. Among the cooling technologies, liquid cooling allows higher cooling circuit temperatures and provides potential for heat recovery. As a thermally driven cooling technology, adsorption refrigeration systems offer an alternative way to compression refrigeration systems by utilizing low-grade waste heat from liquid-cooled circuits to produce chilled water for air-cooled components. In this study, a compact silica gel-water adsorption chiller is developed for a small modular data center and experimentally investigated under extremely low driving temperatures. Under the typical summer conditions with the hot/cooling/chilled water inlet temperatures of 50 °C/30 °C/23 °C, the adsorption chiller achieves the cooling power of 4.9 kW and the COP of 0.50. When the cooling water inlet temperature changes from 32 °C to 24 °C, both the cooling power and COP show significant improvements, from 3.04 kW to 10.50 kW and from 0.44 to 0.66, respectively. Moreover, the increase of the hot water inlet temperature from 48 °C to 56 °C can enhance the cooling power to some extent, while the chilled water inlet temperature has little influence on the performance. The experimental results demonstrate the feasibility and performance of the developed adsorption chiller in data center waste heat driven cooling. Besides, potential adsorbents and possible optimization strategies are presented for performance improvement based on adsorption potential method.

Experimental Investigation of Chilled and Hot Water Inlet Temperature, and Mass Flow Rate Influence on Energy and Exergy Efficiency in a Prismatic Adsorbent Bed Cooling Systems

Adsorption technologies offer a promising solution for managing high electricity demand in building by leveraging waste heat recovery and renewable energy sources. The prismatic adsorbent bed adsorption water cooling system investigates energy and exergy analyses for cooling application. With hot water temperature of 80 °C, cooling water inlet temperature 30 °C, and chilled water inlet temperature 14 °C, the system achieves an energy efficiency of 45.2% while demonstrating an energy storage density of ≈340 kJ kg−1. As a result, the exergy efficiency reaches 12.2%, and the mass fraction at the end of the adsorption process is a significant value of 0.13kgadsorbate/kgadsorbent. Increasing the water mass flow rate in the evaporator results in a decrease in exergy efficiency, while simultaneously causing an increase in energy efficiency. With an increase in the chilled water inlet temperature of the evaporator and the hot water inlet temperature of the adsorbent bed, there is an increase in the energy storage density, energy efficiency, and exergy destruction due to irreversibility and losses. According to this study, the impact of the chilled water inlet temperature on the energy and exergy performances of the evaporator is more significant compared to the effect of the water mass flow rate.

Dynamic performance analysis of a solar adsorption system: the effect of operating conditions and collectors’ area

A continuous adsorption refrigerator, aiming for cold production to a fruit storage room installed in arid regions, is proposed. After cooling load estimation, a technical-economic study of different types of solar collectors was performed. Then, the dynamic performances of a solar-driven two-bed adsorption chiller are studied. Furthermore, this study shows that an optimal choice of the collector-type area and the operating conditions can reduce the global system cost and ensure better energy management. With 43.47 m 2 collectors’ area, a solar fraction of 55% is reached at cycle time (tcycle) 1600s; however, 49% is obtained at tcycle of 900s. With a total collectors’ area of 43.47 m2, a tcycle of 1600s and a cooling water inlet temperature (TCW,in) of 22°C, 60% of the cooling demand is solar produced. However, 57% is achieved at a tcycle of 900s, 50.61 m2 collectors’ area and TCW,in of 25°C. Highlights The cooling load of a storage room used for indigenous fruit preservation was estimated. A technical-economic study of different types of solar collectors is carried out to choose the most suitable one. A detailed dynamic approach to the thermodynamics of a solar adsorption refrigerator according to the time-varying solar radiation intensity and climatic data were presented. The effect of solar collectors’ area and different operating conditions has been studied to optimise the global system performance and cost.

Influence of Cooling Water Parameters on the Thermal Performance of the Secondary Circuit System of a Modular High-Temperature Gas-Cooled Reactor Nuclear Power Plant

This study quantitatively analysed the influence of cooling water parameters on the performance of a modular high-temperature gas-cooled reactor (MHTGR) nuclear power plant (NPP). The secondary circuit system and cold-end system were modelled using EBSILON software, version 16.0. The influence of cooling water inlet temperature and mass flow rate on the thermal performance of the secondary circuit system was analysed over the full power range with the goal of optimising net power. Under 100% rated condition, for each 1 °C increase in cooling water inlet temperature between 10 and 33 °C, the net power and cycle efficiency decreased by 0.67 MW and 0.14%, respectively, whereas the heat consumption rate increased by 28.72 kJ/(kW·h). The optimal cooling water mass flow rates corresponding to cooling water inlet temperatures of 16 °C and 33 °C were obtained. The optimal cooling water mass flow rate decreased nonlinearly with decreasing power levels. At a cooling water inlet temperature of 33 °C, an increase in cooling water mass flow rate from the designed value (7697.61 kg/s) to the optimal value (10,922.14 kg/s) resulted in a 1.03 MW increase in net power. These findings provide guidelines for MHTGR NPP operation optimisation and economic improvement, especially under high-temperature weather conditions.

Experimental research on the effect of acid and ash deposition on heat transfer characteristics of PTFE-coated 3-D finned tube

With characteristics of strong flow disturbance and high heat transfer coefficient, 3-D finned tubes have significant advantages in recovering flue gas waste heat. However, fly ash particles and sulfuric acid vapor in power plant flue gases can foul and corrode 3-D finned tubes when deposited on their wall surfaces, resulting in a reduction in the efficiency of the heat exchanger. To protect the heat exchanger from corrosion, corrosion resistance coatings are the most economical solution. However, acid and ash deposition and their effects on heat transfer performance of the 3-D finned tube coated with corrosion resistance coating have not been clear. In this work, firstly, uncoated, ceramic-coated, Teflon lacquer-coated and PTFE-coated 3-D finned tubes were immersed in sulfuric acid solution and the PTFE coating with better corrosion resistance was screened by corrosion weight loss method and SEM characterization. Then, the heat transfer performance of PTFE-coated 3-D finned tubes under acid-ash coupling conditions was investigated using the simulated flue gas method. Impacts of fin structure parameters (fin height, fin width and axial fin spacing) and experimental working conditions (cooling water inlet temperature, fly ash concentration and sulfuric acid volume fraction) on Nu number were investigated. Results demonstrate that PTFE-coated 3-D finned tube have a lower Nu at the initial moment than uncoated tubes. That is because PTFE coating increases the thermal resistance. However, as the experiment progressed to a steady state, Nu were higher and ash deposition weight was smaller in the PTFE-coated 3-D finned tube. In addition, the effects of fin structural parameters and experimental conditions on heat transfer characteristics of PTFE-coated 3-D finned tube were investigated. In the acid-ash coupled condition, the Nu value increases with an increase of fin height or a decrease of fin width and axial fin spacing. Also, decreasing the cooling water inlet temperature, the fly ash concentration, or the sulfuric acid vapor volume fraction increases the Nu value.

The problem of the surface condenser overall heat transfer coefficient determining at high temperatures of cooling water

The article presents a comparison of the real overall heat transfer coefficient, based on thermal tests of the condenser of the steam turbine PT-25-90 KTZ during off-design operation (with a degraded vacuum) and its expected value, calculated via the Metropolitan Vickers formula. The average cooling water inlet temperature was 61.2 °C, average exhaust steam pressure was 0.542 bar during thermal tests. The average deviation of the expected overall condenser heat transfer coefficient from the real value was 27,18%. The calculations showed a higher difference between the real and expected value at the regimes with low cooling water velocity and with high exhaust stem pressure. The obtained results showed the need to refine the methodology of the condenser's overall heat transfer coefficient calculation in the degraded vacuum mode. This can be done by adding correction factors to the water temperatures that are typical for the degraded vacuum regime.

Optimization of exergetic performance and payback period of organic rankine cycle integrated vapor compression refrigeration system based on exergy, economic, and environmental criteria

In this paper, a multi-objective optimization study is carried out to determine the optimal exergetic performance (𝜂𝑒𝑥) and the payback period (PB) of the organic Rankine cycle (ORC) integrated vapor compression refrigeration (VCR) system based on exergy, economic, and environmental criteria using non-dominated sort genetic algorithm-II (NSGA-II). Moreover, a sensitivity analysis is carried out to improve the exergetic performance of the system. The working fluid, the pinch-point temperature difference of the ORC evaporator (ΔToep ), con-denser (ΔTpcond), and the VCR evaporator (ΔTpve), cooling water inlet temperature (Tcw1), chilled fluid temperature (Tcf2), and heat-source inlet temperature (Th1) are taken as the decision vari-ables. The results of this study indicate that butane is the most suitable working fluid for op-timal exergetic efficiency, 𝜂𝑒𝑥 (33.7%) and payback period, PB (4.9 years) of the system. The optimal values of other decision variables such as Th1, Tcw1, Tcf2, ΔToep , ΔTpve , and ΔTpcondare 378 K, 313 K, 276 K, 10 K, 5 K, and 5 K respectively.

Experimental study on the prevention of microbial fouling accumulation on a Ni-Cu-P modified heat exchange surface

Microbial fouling on heat exchange surface is common for large amount of microorganisms in circulating cooling water. In this article, a modified surface technology is used to suppress and reduce the accumulation of microbial fouling on the heat transfer surface. Firstly a Ni-Cu-P modified surface is prepared by electroless plating, and a Ni-P surface applied commonly in industry is also prepared as a comparison. With the help of the designed and constructed experimental system for dynamic monitoring of microbial fouling, the microbial fouling tests of the Ni-Cu-P, Ni- P and carbon steel surface are carried out. The results show that the Ni-Cu-P modified surface has excellent antifouling performance. Compared with carbon steel, the microbial fouling on the Ni-P and Ni-Cu-P modified surface are decreased by 90.6 % and 92.0 % respectively. Further the effects of temperature, flow rate, and initial bacterial concentration on microbial fouling heat resistance of Ni-Cu-P modified surface are investigated and analyzed. With the cooling water inlet temperature increasing (25–40 °C), the fouling heat resistance of the Ni-Cu-P modified surface is increased first and then reduced. With the flow rate increasing (0.2 m/s-0.3 m/s), the fouling heat resistance of Ni-Cu-P modified surface is decreased by 78.3 %. With the initial bacteria concentration in cooling water increasing (8.364 × 109 CFU/mL −51.456 × 109 CFU/mL), the fouling heat resistance is increased by 57.4 % accordingly. By rationally adjusting the operating conditions, such as regulating the temperature of cooling water far away from the suitable temperature of bacteria and increasing the flow rate of circulating cooling water as much as possible, the accumulation of microbial fouling on the Ni-Cu-P modified surface can be further reduced, allowing for long-term cleaning and effective heat transfer of the Ni-Cu-P modified heat exchange surface.

Steady-state interconnected cycle modeling and experimental results of a lab-scale ORC

ORC is one of the mature technologies for power generation from low temperature heat sources. In this study, the aim is to develop an accurate ORC model which is validated using reliable steady-state data. For this purpose, tests are carried out at four different heat source temperatures ranging from 80 to 110 °C to obtain data in a repeatable manner. The proposed model considers pressure drop and heat transfer correlations to improve the accuracy of model predictions. Using the refrigerant pump mass flow rate, thermal oil pump volumetric flow rate, cooling water inlet temperature, cooling water volumetric flow rate, the throttle valve outlet set pressure, and refrigerant pump outlet pressure as input, the model predicts the pressure, temperature, and mass flow rate in the cycle. The results show that the steady-state ORC model is significantly accurate, with ±1% deviations in pressure and ±1 °C in temperature, and ±5% in mass flow rate, heat transfer rate and refrigerant pump power predictions. The novel iterative model presented in this study includes pipe losses and significantly improves the simulation accuracy of ORCs with long pipes.