Increasing Water Flow Rate Research Articles

Ozone water production using a SPE electrolyzer equipped with boron doped diamond electrodes

Abstract Electrochemical ozone production (EOP) is an attractive technology for disinfection and sterilization purposes. This work reports a study on the EOP performance of the solid polymer electrolyte (SPE) electrolyzer, including the optimization of electrode configuration and operation conditions. It is proven that the EOP performance is highly affected by electrode configuration. Tests using BDDs with different B/C ratios demonstrate that BDD-4.9 provides more reaction sites and faster electron transfer rate, exhibiting a high electrocatalytic activity for EOP. Regarding electrode thickness, 0.54 mm in thickness is the most suitable for the EOP from the perspective of less power consumption. Moreover, operation conditions were evaluated. It was found that increasing water flow rate is an effective strategy for promoting ozone dissolution, and within the present experimental range, the water flow rate of 63 L·h−1 was identified. Meanwhile, through the study of all processes occurring inside the electrolyzer at higher current densities, the optimum current density was determined to be 125 mA·cm−2. Based on these results, ozone water presents excellent performance in the killing of Escherichia coli with high inoculum concentrations, indicating potential application performance in the field of environment.

Experimental study of a natural draft hybrid (wet/dry) cooling tower with a splash fill type

<abstract> <p>Cooling towers have such a significant influence on work and efficiency that researchers and designers are working tirelessly to enhance their performance. A prototype design for a natural draft hybrid (wet/dry) cooling tower has been created, relying on geometrical, dynamic, and thermodynamic similarities. Based on Iraqi weather, experiments have been conducted using splash fill (150 mm) in summer (hot and dry) weather conditions. This study investigated heat transfer mechanisms of both air and water in a natural draft hybrid cooling tower model(NDHCTs), both directly (wet section) and indirectly (dry section). The tower is filled with splash-style packing, and the warm water is spread throughout the building using sprayer nozzles. The influences of water flow rates, fill thickness, and air velocity on the cooling range, approach, cooling capacity, thermal efficiency of the cooling tower, water evaporation loss into the air stream and water loss percentage were explored in this study. The experimental were carried out with four different water flow rates, ranging from 7.5 to 12 (Lpm) litres per minute, and eight different air velocities, all while keeping a constant inlet water temperature and a zero (m/s) crosswind. Data has been gathered, and performance variables have been determined. The findings demonstrate that the cooling tower's efficacy increases when the water flow rate is low, and the cooling range increases with increasing air velocity and decreases with increasing water flow rate; for a 7.5 Lpm water flow rate and a 2.4 m/s air velocity, it expanded to 19.5 ℃. The cooling capacity increased to 23.2 kW for a water flow rate of 12 Lpm and an air velocity of 2.4 m/s.</p> </abstract>

Improving mild steel corrosion resistance in tap water: Influence of water flow and supply rates

The mild steel corrosion has been studied in hot tap water (50 °C) using linear polarization technique in the laboratory set-up that models water circulating system. The influence of water flow rate (0.15–0.45 m/s) and water supply rate (0–70 % of system volume per hour) on corrosion kinetics have been investigated. The corrosion products, formed on the surface of the steel corrosion probes, have been analyzed with XRD. It has been found, that in condition of low water flow rate (0.15 m/s) and in the absence of water supply the corrosion rate is high (0.29 mm/year) due to low blocking abilities of the surface deposits. Amorphous Fe(OH)3 is the main corrosion product to be detected on the surface. The increase in water flow rate above 0.15 m/s and water supply rate above 30 % of system volume per hour leads to the 1.6 times corrosion rate reduction (to 0.18 mm/year) due to the formation of dense surface layer of calcium carbonate and iron oxyhydroxides. The results obtained can be utilized to improve the corrosion performance of hot water supply systems.

COMPARISON OF OPTIONS FOR THE HEAT DISTRIBUTION NETWORK OF THE RESIDENTIAL NEIGHBORHOOD

The comparison of heat losses by pipelines of an extensive residential neighborhood heating system for two options of the distribution network was carried out for a residential neighborhood in Kharkov. The proposed configuration of the heating network differs from the existing ("basic") one in using of the law of heating medium flow rate variation along the heat pipe length. This law takes into account increased flow rate of heating water through branches at the initial sections of the pipeline. The actual flow rate distribution is approximated by a step function. The difference in the laws of flow rate variation is taken into account by the exponent value. The calculation of heat losses was carried out for underground pipelining in non-accessible tunnels. The temperature of heat line water is taken to be the corresponding to the design outdoor air temperature for heating according to the temperature schedule of the heating network. Specific heat losses by pipelines in heat network sections are considered to be at the standard level for non-accessible tunnels. The soil temperature at the depth of the heat pipe axis is taken equal to 5°C. Heat losses by the structural elements of the heat network are taken into account by a factor of 1.15. The variation of the flow rate and temperature of network water in rated pipeline sections is considered in the analysis. The water flow rate at the sections was found based on the design thermal loads of connected buildings.
 It is shown that when choosing the configuration of the distribution network of the heating system of a group of buildings, preference should be given to the option with a lower value of the exponent in the equation for heating medium flow rate variation along the length of the main line of the network. For extensive heating networks, this can be achieved by connecting as many buildings as possible to the heating network sections close to a heat supply station. An increase in the network water flow rate through the branches at the initial sections of the pipeline ensures a decrease in heat losses by the network pipelines. For the considered part of a residential neighborhood, the decrease in heat loss at the design outdoor air temperature for heating is 5.5 %.

Computational Studies of Air-Mist Spray Cooling in Continuous Casting

Due to the significant reduction in water droplet size caused by the strong air-water interaction in the spray nozzle, air-mist spray is one of the promising technologies for achieving high-rate heat transfer. This study numerically analyzed air-mist spray produced by a flat-fan atomizer using three-dimensional computational fluid dynamics simulations, and a multivariable linear regression was used to develop a correlation to predict the heat transfer coefficient using the casting operating conditions such as air-pressure, water flow rate, casting speed, and standoff distance. A four-step simulation approach was used to simulate the air-mist spray cooling capturing the turbulence and mixing of the two fluids in the nozzle, droplet formation, droplet transport and impingement heat transfer. Validations were made on the droplet size and on the VOF-DPM model which were in good agreement with experimental results. A 33% increase in air pressure increases the lumped HTC by 3.09 ± 2.07% depending on the other casting parameters while an 85% increase in water flow rate reduces the lumped HTC by 4.61 ± 2.57%. For casting speed, a 6.5% decrease in casting speed results in a 1.78 ± 1.42% increase in the lumped HTC. The results from this study would provide useful information in the continuous casting operations and optimization.

IMPROVING MILD STEEL CORROSION RESISTANCE IN TAP WATER: INFLUENCE OF WATER FLOW AND SUPPLY RATES

The mild steel corrosion has been studied in hot tap water (50 °C) using linear polarization technique in the laboratory set-up that models water circulating system. The influence of water flow rate (0.15-0.45 m/s) and water supply rate (0-70 % of system volume per hour) on corrosion kinetics have been investigated. The corrosion products, formed on the surface of the steel corrosion probes, have been analysed with X-Ray Diffraction (XRD). It has been found, that in condition of low water flow rate (0.15 m/s) and in the absence of water supply the corrosion rate is high (0.29 mm/year) due to low blocking abilities of the surface deposits. Amorphous Fe(OH)3 is the main corrosion product to be detected on the surface. The increase in water flow rate above 0.15 m/s and water supply rate above 30 % of system volume per hour leads to the 1.6 times corrosion rate reduction (to 0.18 mm/year) due to the formation of dense surface layer of calcium carbonate and iron oxyhydroxides. The results obtained can be utilized to improve the corrosion performance of hot water supply systems.

Experimental and theoretical study on strengthening mechanism of coarse coal slime classification process with cone wall structure

The accurate classification of coarse coal slime is the premise of efficient separation. Deep Cone Hydraulic Classifier (DCHC) is a new classification equipment for coarse coal slime classification, the content of fine particles (-0.2 mm) in coarse coal slime can be effectively reduced through classification, so as to create suitable feeding granularity for teetered bed separator (TBS) sorting. The DCHC designed includes a column structure area, deep cone structure area, and flush water mode of “bottom water + central water”. Experiments on the impact parameters were carried out, the results showed that: the classification efficiency increased with the decrease of feed concentration and feeding speed, increased first and then decreased with the increase of flush water flow rate. When the feed concentration was 40%, feeding speed is 0.8 m/s and flush water flow rate was 4 m3/h, the classification efficiency reached 69.3%, the content of the −0.2 mm particles in the bottom flow products was only 1.9%. The classification mechanism showed that the column structure area realized fluidization of the flow field and the deep cone structure area supplied the movement trace for the particles. Particularly the −0.074 mm particles movement trace was clear along the cone wall and could be collected as an overflow. A part of the −0.125 mm particles could be collected as an overflow, whereas the remaining part returned to the bottom flow, and increased fine particles content. In addition, the +0.2 mm particles were mostly collected as a bottom flow, and the 0.2–0.3 mm particles content are obviously affected by operating parameters. The results not only provide a new idea for the development of new classification equipment, but also provide a pathway for the efficient classification of coarse coal slime.

Performance of reduction on particle emission by combining the charged water drop atomization and electric field in wet electrostatic precipitator

In this study, a wet electrostatic precipitator (WESP) with combination of electric field and charged water drop atomization was designed for fine particle collection, which replaced the traditional water film and mechanically spray. The removal performance was evaluated considering applied voltage, water flow rate, gas residence time, dust concentration, and continuous operation time. Results indicated that supplying charged droplets could acquire higher discharge current and better agglomeration effect than the dry type. The maximum penetration ratio was reduced from 3.8%−11.56% in the dry ESP to 3.58%−8.6% with charged droplets, as the applied voltage increased from 30 kV to 60 kV. Meanwhile, increase of water flow rate improved the total removal efficiency. The advantage of the WESP was more obvious under short gas residence time. The route of synergistically increasing gas residence time and applied voltage could largely reduce the penetration ratio, which decreased from 6.99%−19.81% to 1.03%−2.43% as they were enhanced from 1.50 s and 30 kV to 3.33 s and 60 kV. Increasing the dust concentration led to the trend that the total removal efficiency first increasing and then decreasing gradually, resulted from combined mechanisms of particle agglomeration and suppression of corona current. Moreover, the atomization of charged water drop maintained the advantage on particle removal under continuous operation, and the efficiency drop after long-term operation could be avoided. In particular, the WESP achieved significant reduction on water consumption compared to conventional large-scale and on-site WESPs in application with equivalent levels of removal efficiency.

Discrete-Particle Model to Optimize Operational Conditions of Proton-Exchange Membrane Fuel-Cell Gas Channels.

Operation of proton-exchange membrane fuel cells is highly deteriorated by mass transfer loss, which is a result of spatial and temporal interaction between airflow, water flow, channel geometry, and its wettability. Prediction of two-phase flow dynamics in gas channels is essential for the optimization of the design and operating of fuel cells. We propose a mechanistic discrete particle model (DPM) to delineate dynamic water distribution in fuel cell gas channels and optimize the operating conditions. Similar to the experimental observations, the model predicts seven types of flow regimes from isolated, side wall, corner, slug, film, and plug flow droplets for industrial temporal and spatial scales. Consequently, two-phase flow regime maps are proposed. The results suggest that an increase in water accumulation in the channel is related to the increase in the water cluster density emerging from the gas diffusion layer rather than the increased water flow rate through constant water pathways. From a modeling perspective, the DPM replicated well volume-of-fluid channel simulation results in terms of saturation, water coverage ratio, and interface locations with an estimated 5 orders of magnitude increase in calculation speed.

Numerical simulation of the solidification process of Cu-0.45% Sn alloy in upward continuous casting

Upward continuous casting is the key process in the production of contact wire for electric railway. The stability of the process and the quality of the produced billet are directly related to the performance of the contact wire and ultimately the safety of the railway operation. To ensure the quality of continuous-casting billet, the optimal process conditions need to be experimentally determined, which is not only costly but also time-consuming. To facilitate this optimisation process, the simulation of the solidification process of Cu-0.45%Sn alloy in upward continuous casting is described in this paper to assess the influence of casting temperature, upward continuous casting speed, the time of stop-pull, and primary cooling water flow rate on the liquid core length. The results show that the speed of upward continuous casting exhibits a great influence on the liquid core length, while the casting temperature has only little influence. In a certain range of the ratio of stopping time to pulling time, the quality of updraft Cu-0.45%Sn alloy billet is improved; exceeding a certain ratio results in a decrease of the surface quality and an increase in internal and external defects. The liquid core length of the continuous casting rod decreases with the increase of the cold water flow rate, and properties are stable when the flow rate reaches 0.45 m3·h−1. For a billet with a diameter of 20 mm, the appropriate upward continuous casting process parameters are determined as a casting temperature of 1175 °C, an upward continuous casting speed not exceeding 25 cm·min−1, a ratio of stopping time to pulling time not exceeding 2.13, and a cooling water flow rate of 0.45 m3·h−1.

Performance Enhancement of Split Air Conditioner During Evaporative Cooling Application

The increase of condenser temperature and pressure in air-conditioning leads to decreased cooling capacity and the increase of power consumption. Evaporative cooling could improve the thermal performance of the system. In this study, the evaporative cooling module was installed before the condenser to reduce the inlet air temperature to the condenser unit. The impact of condenser air temperature on the air conditioning system's overall performance was determined by varying the cooling pad discharge water flowrate of 880, 1040, and 1200 mL/min. The cooling load of 2000 W was employed in this experiment. The obtained results were compared with the air conditioning without an evaporative cooling module. It shows that the coefficient of performance (COP) increases with the increase of discharge water flow rate. The highest COP obtained is 7.09 at the flow rate of 1200 mL/min. The compressor work reduces about 6.57 % as compared with the air conditioner without evaporative cooling application. Besides, the COP increases by 12. 95 % at the highest flow rate.

An investigation on the bubble transportation of a two-stage series venturi bubble generator

In this paper, we designed a new venturi bubble generator, which mainly consist of two serial rectangular perspex venturi channels with the same geometrical dimension. Visualization experimental method combined with digital image analysis was adopted to study the motion, deformation and breakup process of bubbles when the micro-bubble generator was installed vertically. The bubble foaming frequency which is defined as the amount of forming bubbles within one second from the air injection hole was significantly enhanced with the increase of water flow rate, but was not sensitively affected by the air flow rate. The discrete bubbles moved in a two-stage venturi channel and experienced collapse or breakup in the divergent section. The Sauter mean diameter of bubbles which recorded in each divergent outlet decreased gradually. The Reynolds numbers of water had a significant effect on the breakup characteristics of bubbles. With the increasing of Re, the bubbles experienced binary breakage and multiple breakup successively. Under the effect of complex turbulence vortex, the bubbles presented different breakup patterns in each stage. When Reth>19793, the bubble breakup ratio of the first stage divergent section was larger than that of the second stage, and the difference of the generated bubble Sauter mean diameter in each divergent outlet was minimized accordingly. The surface stability of the daughter bubble was enhanced, and it was difficult to breakup significantly under the effect of recirculation flow. The numerical simulation results by Computational Fluid Dynamics (CFD) indicated that the area of the vortex was increased for larger second stage divergent angle, which intensify the phase interaction and promote the possibility of sub-micron bubble breakup.

Experimental investigation of hydrothermal characteristics of data center servers’ liquid cooling system for different flow configurations and geometric conditions

Due to the rapid growth of power densities of modern electronics devices and data centers servers, liquid cooling using heatsink/cold plate technique become prevalent than air cooling technique of data centers. In the present paper, effects of cold plate flow configurations and geometric parameters on the hydrothermal characteristics of servers liquid-cooling were experimentally investigated. Experiments were conducted at wide ranges of operating conditions and geometric parameters such as server power density, water flow rate, water temperatures, parallel and serpentine flow configurations, number of flow channels and cold plate thicknesses. Thermal resistance, average server temperature, Nusselt number, pressure drop and pumping power are used as measuring perfromance parameters for servers cooling. Experimental correlations are deduced to predict the perfromance parameters in terms of the operating conditions and geometric parameters. Results showed a decrease in thermal resistance and servers' temperature and an increase in Nusselt numbers, pressure drop and pumping power with increasing water flow rate and decreasing water temperature. Also, it was found that serpentine flow configuration has a better thermal performance and a worst hydrodynamic perfromance compared to parallel flow configuration. Increasing number of flow channels and decreasing base thickness of the cold plate provide a better thermal performance on the expense of hydrodynamics perfromance. Using serpentine flow configurations instead of parallel flow and increasing the number of flow channels form 8 to 12 reduce the water flow rate needed to maintain the servers’ temperature within the allowable limit by 69 % and 91 % and increase pumping power by 95 % and 50 %, respectively.

Effect of Water Flow on Underwater Wet Welded A36 Steel

Underwater wet welding (UWW) combined with the shielded metal arc welding (SMAW) method has proven to be an effective way of permanently joining metals that can be performed in water. This research was conducted to determine the effect of water flow rate on the physical and mechanical properties (tensile, hardness, toughness, and bending effect) of underwater welded bead on A36 steel plate. The control variables used were a welding speed of 4 mm/s, a current of 120 A, electrode E7018 with a diameter of 4 mm, and freshwater. The results show that variations in water flow affected defects, microstructure, and mechanical properties of underwater welds. These defects include spatter, porosity, and undercut, which occur in all underwater welding results. The presence of flow and an increased flow rate causes differences in the microstructure, increased porosity on the weld metal, and undercut on the UWW specimen. An increase in water flow rate causes the acicular ferrite microstructure to appear greater, and the heat-affected zone (HAZ) will form finer grains. The best mechanical properties are achieved by welding with the highest flow rate, with a tensile strength of 534.1 MPa, 3.6% elongation, a Vickers microhardness in the HAZ area of 424 HV, and an impact strength of 1.47 J/mm2.

Experimental investigation of trajectories, velocities and size distributions of bubbles in a continuous-casting mold

A ¼-scale water-model experiment is conducted to investigate the trajectories, velocities and size distribution of bubbles in a continuous-casting mold. A high-speed camera and a laser are used to record the transient bubble distribution. The region of interest is delimited to include the motion range of floating bubbles in the upper mold, and divided into 70 subregions of seven rows and 10 columns. Information on the trajectories, velocities and size distributions of bubbles is obtained from image sequences, using the ImageJ software. The effects of water/gas flow rates on the transport and size distribution of bubbles are studied. The results show that the motion range of larger bubbles decreases toward the submerged entry nozzle (SEN) and the floating direction of larger bubbles moves closer to vertical. The increase in water flow rate increases the level transportation distance of bubbles along the jet flow and the intensity of upper circulation flow, which has a complex effect on bubble transportation near the SEN. An increase in the gas flow rate contributes to the ascending flow near the SEN and significantly increases the bubble number in the region of interest for the entire bubble-diameter range, without causing an increase in mean bubble diameter.

Enhancing the thermal performance of a photovoltaic panel using nano-graphite/paraffin composite as phase change material

In this study, a nano-graphite/paraffin composite is used to augment the cooling performance of a PV panel, which significantly increases the output power due to decreasing the thermal stresses and current mismatching problems. The constructed composite is a phase change material (PCM). In order to retard the melting of PCM, a finned tube-heat exchanger is inserted inside the PCM. At first step, pure paraffin and finned tube-heat exchanger are used for cooling of a PV panel and secondly, graphite nanoparticles (ϕ = 0.002–0.012 (w/v)) are combined with PCM. The results of temperature, voltage–ampere curves and the maximum power output of the PV panel using PCMs are compared with no cooling device. Results show that using the nano-graphite/paraffin composite has significantly added benefits over using pure paraffin. By increase in water flow rate, the surface temperature of the PV panel is decreased because of increase in the heat transfer rate between the water and PCM around the tubes. Average surface temperature of the PV module is reduced from 336.15 to 310.25 K by using nano-graphite PCM with ϕ = 0.01 (w/v) and the highest value of water flow rate (Q = 100 mL s−1). The maximum enhancement in the power output of the PV/nano-PCM system by using the efficient conditions is 21.2%. The proposed system not only boosts considerably the output electrical power, but also reduces the PV panel temperature while keeping it uniform for each cell.

Geometrical Optimization of a Venturi-Type Microbubble Generator Using CFD Simulation and Experimental Measurements

Microbubble generators are of considerable importance to a range of scientific fields from use in aquaculture and engineering to medical applications. This is due to the fact the amount of sea life in the water is proportional to the amount of oxygen in it. In this paper, experimental measurements and computational Fluid Dynamics (CFD) simulation are performed for three water flow rates and three with three different air flow rates. The experimental data presented in the paper are used to validate the CFD model. Then, the CFD model is used to study the effect of diverging angle and throat length/throat diameter ratio on the size of the microbubble produced by the Venturi-type microbubble generator. The experimental results showed that increasing water flow rate and reducing the air flow rate produces smaller microbubbles. The prediction from the CFD results indicated that throat length/throat diameter ratio and diffuser divergent angle have a small effect on bubble diameter distribution and average bubble diameter for the range of the throat water velocities used in this study.

Effect of material on fluid elastic instability of parallel triangular tube array subjected to water cross

The effect of tube material and structure on fluid elastic instability is examined experimentally using a parallel triangular finned tube array with a P/D ratio of 1.78. Flow-induced vibration is a common cause of failure in shell and tube heat exchangers, and it may result in substantial harm to the heat exchanger as well as significant financial loss. There are different mechanisms responsible for flow induced vibration out of which fluid elastic instability and vortex shedding are the most severe due to their sudden occurrence and high amplitude of vibration. Different parameters affect the tube vibration when the tube array is subjected to water crossflow. In this paper effect of tube material and fin are examined for fluid elastic instability. Experimentation was performed to measure demanding velocity at fluid elastic instability for plain and finned tubes for steel, aluminum and copper material. A fully flexible tube array with a cantilever end condition and with a constant pitch ratio subjected to water cross flow was considered. Testing was done with a gradually increasing water flow rate from 5 m3/hr and increases up to 75 m3/hr to obtain fluid elastic instability. The relationship between the critical velocity at fluid elastic instability and the mass damping parameter was investigated using Connor's equation. The amplitude response of vibration concerning the change in velocity shows that the addition of fins, as well as the material change, greatly affects the fluid elastic instability. A small peak before the occurrence of fluid elastic instability was observed. This is maybe due to vortex shedding which further required to be verified using the Strouhal number.

Experimental study of the characteristics of gas-injection barrier in two-dimensional porous media

The inflow of groundwater into the oil shale in-situ pyrolysis zone reduces the heating efficiency and has negative impacts on soil ecology and drinking water safety. Thus, we propose a sealing system for oil shale in-situ pyrolysis exploitation with a gas-injection barrier. In this study, the characteristics of gas-injection barrier were investigated comprehensively in the two-dimensional porous media. First, the evolution and distribution of hydraulic conductivity were studied. Results showed that gas injection promoted water flow in the central subregion when the gas flow rate was less than 50 mL/min. With a further increase in the gas flow rate, a significant inhibition effect on the water flow within all subregions was achieved. Then, the gas-injection barrier mechanism was quantitatively analyzed, showing that a pressure-balanced state in the extended front of the upstream gas flow served as one mechanism when a larger gas flow rate was reached, which was verified by experiments for the first time. Finally, the distribution of the gas flow fitted by a Gaussian curve was explored. In addition, the sensitivity of hydraulic conductivity was discussed; with increasing water flow rate and the coarsening of glass beads, the relative hydraulic conductivity improved comprehensively. All results obtained are conducive to a comprehensive understanding and application of the gas-injection barrier.

Numerical and experimental investigations of the micro-channel flat loop heat pipe (MCFLHP) heat recovery system for data centre cooling and heat recovery

This paper represented a dedicated study of the effects of coolant water flow on the performance of the micro-channel flat loop heat pipe (MCFLHP) heat recovery system using both theoretical and experimental methods. The MCFLHP heat recovery system is novel in the micro-channel flat plate evaporator of the loop heat pipe attached tightly to the heat generator of the IT equipment and the micro-channel flat plate condenser of the loop heat pipe installed outside the data cabinet, which realises the long distance heat removal from the inside of the data cabinet to the outside and reduces the energy consumptions in the data centre. This system adopted the separate evaporation and condensation structures, which were connected into a complete loop through vapour transmission line and liquid return line, and employed the heat exchange part and chiller part as the heat recovery devices. Taking into account the heat balances occurring in different parts of the system, a computer model was developed to predict the dynamic performance of the MCFLHP heat recovery system 8 at different coolant water flow rates when other working conditions were unchanged. Experiments were also conducted to validate results obtained from the simulation. Through comparison between the testing and modelling results, the model has been validated to be able to give a reasonable accuracy for predicting the performance of the MCFLHP heat recovery system. It was found that the heat recovery efficiency increased firstly and then decreased with the increase of the coolant water flow rate, and 300 L/h was the most optimal coolant water flow rate for the proposed system. The instantaneous heat recovery efficiency of the MCFLHP heat recovery system was maintained within 81–94% under the optimal coolant water flow rate when the system was running stably, and the average efficiency was at 84.06%.