Performance Of Heat Exchanger Research Articles

Harnessing the heat below: Efficacy of closed-loop systems in the cooper basin, Australia

Transitioning to renewable energy is vital for combating climate change and reducing CO2 emissions. Geothermal energy, sourced from the earth's crust, presents a promising alternative. While shallow geothermal energy extraction grows steadily, tapping into deep Hot Dry Rock reservoirs poses challenges. Sustainable utilization of deep geothermal energy is crucial for large-scale electricity generation. Australia's Habanero enhanced geothermal system (EGS) projects faced obstacles due to complex fracture networks. Borehole heat exchangers (BHEs) offer a solution, circulating a working fluid without direct contact with geofluids. This study assesses coaxial BHEs' feasibility in the Habanero reservoir using a 2D axisymmetric model (2D-AM), comparing it with a simpler 1D depth-integrated model (1D-DIAM). Both models yield similar outcomes. Additionally, results indicated that the production temperature of the coaxial BHE exponentially decreased from 250 °C to 100 °C within 10 h, rendering energy recovery for electricity generation unsuitable after 10 h of operation. The study proposes an energy recovery cycle of 10 h followed by a 110-h shutdown. Injection temperatures and flow rates significantly impact production efficiency, while steel casing's thermal conductivity has minimal influence on heat exchanger performance.

Optimization of heat transfer in PCM based triple tube heat exchanger using multitudinous fins and eccentric tube

This study aims to analyze the effect of incorporating a hybrid concept of heat transfer enhancement using extended surfaces and eccentricity of the inner tube in an RT-82 phase change material-based horizontal triple tube heat exchanger. Three types of fins were used, namely longitudinal, arc and triangular shape fins, as per suitability for better heat transfer. Moreover, the concept of eccentricity was also implemented to make PCM melt faster. The novelty of the present study lies in optimizing the heat transfer enhancement by proper placement of the fins and eccentric inner tube arrangement. A conduction-convection model was used to examine the thermal performance of a triple tube heat exchanger. The natural convection of PCM was employed using the Boussinesq approximation. The governing equations were solved using finite volume-based Ansys Fluent 2021 R2 software. The performance study of phase change material was based on transient variation of liquid fraction and average temperature. The optimum model showed a 63.87 % reduction in melting time and a 175.16 % improvement in heat transfer rate compared to a simple triple tube heat exchanger to achieve the unit liquid fraction. It is also observed from the calculation of the Rayleigh number that the conduction became more dominant than the convection phenomenon in the fin based model. The main finding of the present study is the use of triangular fins on the base along with the curved fins at the lower middle section because this arrangement shows high heat penetration capability. The results indicate that fins selection and placement significantly enhance the heat transfer rate.

Novel Correlations for flow and heat transfer processes in S-CO2 Brayton cycle with different roughness by experimental and simulation methods

This study comprehensively examines heat transfer performance of supercritical carbon dioxide (S-CO2) in horizontal tubes under actual operating conditions of precooler, regenerator and heater, with a focus on the impact of tube roughness. By employing both experimental and numerical methods, it aims to bridge the gap in current research regarding S-CO2 heat exchanger performance that incorporates the effect of roughness. The results indicate that roughness height can suppress the influence of buoyancy effects. As roughness height increases from 1.5 μm to 100 μm, average temperature difference of heater at an outlet temperature of 1000 K decreases from 134.9 K to 61.1 K. Although roughness height can significantly enhance heat transfer, yet the rate of this enhancement diminishes when the roughness height surpasses 50 μm. To address the need for accurate heat transfer and flow correlations considering roughness, high-precision correlations are proposed and validated. The correlations of precooler, regenerator and heater exhibit average absolute deviations of within 8 %, 10 % and 12 %, respectively. The proposed correlations not only enrich theoretical framework of related fields but also provide a solid foundation for optimizing the design and operation of S-CO2 Brayton cycle, enabling more efficient energy conversion and reduced carbon emissions.

Effect of air bubble injection on the thermal performance of a vertical helical coiled tube heat exchanger: an experimental study

This study investigates the effect of air bubble injection on the thermal performance of a vertical counter-current coiled tube heat exchanger. A cylindrical PVC shell (height: 500 mm, diameter: 152.4 mm) was constructed to carry a copper coil with 11 regular turns and covered approximately 76% and 75% of the total shell height and diameter, respectively. The key operational parameters involving the shell side flow rate (2–10 L/min), the coil side flow rate (1–2 L/min), the air flow rate (0–10 L/min) and the temperature difference between the hot and cold fluids ((20 °C, 30 °C and 36 °C) were tested to determine the overall heat transfer coefficient (U). Air was injected into the shell side of the heat exchanger as bubbles with an average diameter of approximately 100 μm via a porous sparger. The results showed that air injection significantly enhanced U, with the highest improvement (158%) occurring at an air flow rate of 6 L/min, while the minimum improvement was 34%. Furthermore, the ratio of the overall heat transfer coefficient with air injection to that without air injection had its maximum value at a shell side flow rate of 6 L/min.

Numerical and experimental investigation of additive manufactured heat exchanger using triply periodic minimal surfaces (TPMS)

With the increasing demand for high-efficiency compact heat exchangers in automobiles and spacecraft, lighter and more efficient metamaterials hold promise as advanced materials for cooling applications but remain beyond reach. Triply Periodic Minimal Surface (TPMS) structures, characterized by their smooth surfaces and significantly huge volumetric surface area, represent ideal internal structures for heat exchangers, and the development of additive manufacturing has made their design and production possible. This study focuses on designing heat exchangers based on seven TPMS structures (Fischer-Koch S, Gyroid, SplitP, Diamond, I-WP, F-RD, Primitive) and prints the finished heat exchangers using AlSi10Mg material based on numerical investigation results. Comprehensive evaluation metrics are used to rank the results. The findings reveal that the internal interleaved channels have varying effects on different structures, with Fischer-Koch S exhibiting the highest heat transfer capability of up to 269 W/K. Gyroid and I-WP demonstrate the best fluidity, with resistance only 23.44 % of Primitive’s. Gyroid has the best overall evaluation metrics, with a 54 % efficiency improvement over traditional plate heat exchangers. Additionally, this study proposes the use of the Voronoi algorithm to handle the channels of TPMS and identifies the asymmetric characteristics of heat exchangers on both sides, and it is believed that there is still greater optimization potential for the performance of TPMS heat exchangers

Effects of extended pin fins on the hydrothermal performance of double pipe heat exchanger

Double pipe heat exchangers (DPHEs) are crucial for effective heat transfer between two fluids in industrial processes, enhancing energy recovery and optimizing thermal performance. This study aims to enhance the efficiency of DPHEs by incorporating extended pin fins. DPHEs are vital in industrial applications for their efficient heat transfer, but optimizing their performance remains challenging. Extended pin fins, which are minor protrusions added to the heat exchanger’s surface, increase the surface area for heat transfer. A numerical study on DPHEs with pin fins of varying length ratios (R=1, 2, 3, and 4) is conducted, validating our model by comparing results with prior experimental data. Parameters such as Nusselt number (Nu), friction factor, thermal–hydraulic performance factor (TPF), and exergy efficiency across Reynolds numbers from 4400 to 9400 are calculated. The results indicate that pin fins significantly enhance heat transfer. The Nu increases by 163 %-242 % for different length ratios, while the friction factor decreases, showing reductions of 161 %-290 %. Exergy efficiency improves by 216 % with an R=4 design compared to a standard DTHE, and the TPF increases by 152 % with the R=4 configuration. These findings demonstrate the substantial benefits of using extended pin fins in improving the thermal performance of DPHEs.

Research on heat exchanger tube sheet to shell fillet weld testing and engineering application using total focusing phased array technique

Abstract According to structure of the heat exchanger tube sheet to shell fillet weld, the total focusing phased array technique was adopted to settle down this testing difficulty. Firstly, the inspection background and detection difficulties of the fillet weld was introduced in this paper. Secondly, the sound field simulation and typical flaw response simulation was carried out using CIVA software, and the special blocks were manufactured on the base of the simulation result. Thirdly, the total focusing phased array testing study was carried out in laboratory, and the drilled holes, grooves, as well as the typical flaws of incomplete fusion, incomplete penetration and crack in blocks were successfully detected. Finally, the total focusing technique engineering application of one heat exchanger in chemical device was put into effect, the incomplete fusion and incomplete penetration flaws were successfully detected. The total focusing phased array technique was successfully applied to the heat exchanger inspection project, the research result of this paper have high practical value for ensuring the safe and reliable operation of heat exchanger, and can be popularized and applied in the engineering project.

Study on the influence law of vortex generating structure on heat transfer performance of heat storage device

Solar energy is emerging as a resilient and environmentally friendly energy source. Utilizing heat storage devices to capture solar energy not only reduces carbon emissions but also aligns with the broader goal of energy conservation. In the effort to optimize the heat transfer efficiency of trough solar heat storage devices, a comprehensive investigation was conducted. This study involved the systematic design and analysis of twelve distinct structures, each characterized by varying contact angles and eccentricities. It was observed that using a substantial contact angle of Δ=0.2R (θ=150°) induces a stable disturbance within the pipeline, thereby significantly enhancing the overall heat transfer performance. Building on this observation, seven different eccentric structures were systematically designed to further improve the heat exchange performance of the pipeline. The findings indicate that, particularly at high Reynolds numbers, the implementation of an eccentric structure markedly enhances the heat transfer performance of the pipeline. Additionally, when Δ=0.2R, it effectively contributes to the improvement in the efficiency of heat storage devices.

Self-assembled nanoflower-mediated interfacial polymerization through tunable intra- and inter-layer channels to boost total heat exchange performance

Total heat exchange membranes (THEMs) are vital for minimizing energy consumption and enhancing indoor air quality in energy recovery ventilation (ERV) systems. Manipulating the surface morphology of polyamide (PA) membranes via nanofiller-mediated interfacial polymerization is key to advancing total heat recovery performance. This study presented the fabrication of PA thin-film nanocomposite (TFN) membranes by integrating self-assembled poly(amic acid-imide) nanoflowers (P(AA-I)-NFs) with intertwined nanosheets into the organic phase. This facile approach effectively eliminated nonselective interphase voids and defects, owing to the superior polymer affinity of the organic nanoflowers. The finely tuned intra- and inter-layer channels within P(AA-I)-NFs significantly impacted monomer mass transfer, facilitated the shuttle effect, expanded the interfacial polymerization zone, and led to the formation of a rougher, thicker PA layer with enhanced surface area. The optimized P(AA-I)-NFs/PA TFN membranes exhibited outstanding performance, including CO₂ permeability of 0.51 GPU, water vapor permeability of 656.59 GPU, and an enthalpy exchange efficiency of 71.47 %, surpassing the trade-off limitations typically observed in commercial and other advanced THEMs. These findings underscored the potential of P(AA-I)-NFs-mediated TFN membranes as highly competitive candidates for next-generation ERV systems.

Numerical Investigation of Thermal Performance Enhancement in a Newly Designed Shell and Tube Heat Exchanger using 〖"TiO" 〗_"2" Nanofluids

This study investigates the use of titanium dioxide (TiO2) nanofluids to enhance the thermal performance of shell and tube heat exchangers. A comparative computational fluid dynamics (CFD) analysis is conducted using water and a 0.5% TiO2 nanofluid. The heat exchanger is modelled using computer-aided design (CAD), with dimensions closely resembling commercial units. The CFD model is validated through a grid-independence study, with a mesh of 4,112,679 elements yielding grid-independent results. The key findings show that the 0.5% TiO2 nanofluid increases the cold fluid outlet temperature by 11.44% compared to water (36.04°C vs. 33.63°C). The average heat transfer coefficient is enhanced by 12.3% when using the nanofluid. The CFD results are consistent with experimental data, with a maximum deviation of 4.2% in the outlet temperatures. This study demonstrates the successful integration of TiO2 nanofluids with an optimized shell and tube heat exchanger design. The novelty lies in the application of nanofluids to improve the thermal performance of industrial heat exchangers. The presented methodology, combining CAD modelling and CFD analysis, provides a foundation for further optimization and experimental validation of nanofluid-enhanced heat transfer systems.

A method to calculate the two-phase distribution in a microchannel heat exchanger

Maldistribution seriously impacts the heat transfer performance of the microchannel heat exchanger (MCHX). Fully understanding the two-phase distribution in the heat exchanger is important for advancing academic research and engineering applications. This study introduces a novel method for quantifying two-phase distribution in a microchannel heat exchanger. An experimental setup was developed to measure the local vapor mass fraction in the heat exchanger header. Capacitance signals were measured under inlet vapor mass fractions from 0 to 1, and inlet flow rates of 10, 15, and 25 g s−1 corresponding to a mass flux of 17.47, 26.2, and 43.66 kg m−2s−1, respectively. The local vapor mass fraction in the header was estimated using the capacitance measurements. The mass flow rate in the header, the microchannel tube, and the vapor mass fraction in the tube were calculated using the proposed model. The calculation model was validated against literature data, and the results were analyzed. The analysis reveals the characteristics of vapor mass fraction and mass flow rate distribution in the MCHX and further elaborates on the effects of phase separation, entrainment ratio, and pressure drop balance on the distribution. The proposed method can evaluate distribution in the header and tubes of microchannel heat exchangers, and it is also applicable to other types of two-phase flow devices.

Composites with Synergistically Enhanced Thermodynamic and Mechanical Properties for Geothermal Heat Exchangers

Geothermal energy, derived from the radioactive decay of elements within the Earth's core, is a renewable and clean energy source. The extraction of geothermal energy primarily depends on ground heat exchangers. To address the issue of incompatibility between corrosion resistance, high thermal conductivity, and mechanical performance in current ground heat exchangers, this study develops composites (PEPOE/SCA@SiC) composed of high‐density polyethylene (HDPE) modified with toughener polyethylene‐octene copolymer elastomer (POE) and silicon carbide (SiC) crystals modified with γ‐aminopropyltriethoxysilane (SCA). HDPE offers excellent corrosion resistance, SiC crystals provide efficient phonon transport, and SCA improves the interface compatibility of the composite. The thermal conductivity of PEPOE/SCA@SiC reaches 3.83 W m−1K−1, with a maximum tensile strength of 20.3 MPa, a tensile elastic modulus of up to 498 MPa, and a maximum bending stress of 22.2 MPa with a bending elastic modulus of 561 MPa. Corrosion resistance tests indicate no signs of corrosion in PEPOE/SCA@SiC when exposed to geothermal simulation fluids at 90 °C for 30 days. This study demonstrates that PEPOE/SCA@SiC composites have substantial potential for application in ground heat exchangers, offering promising prospects for advancing sustainable use of geothermal energy and environmental protection.

Experimental study on the heat storage characteristics of rock bed heat storage system with different packing structure

Establishing energy storage systems can provide an effective solution to the challenges posed by the variability and intermittency of renewable energy sources. Among the available options for energy storage, rock-packed bed thermal energy storage systems are widely favored for their performance, cost-effectiveness, and reliability. The more compact the rock packing, the more adequate the heat exchange of the system; however, poorer permeability increases fluid friction losses and pressure drop, which is detrimental to heat transport within the system. The permeability and heat exchange of the system jointly determines its thermal energy storage performance. This study proposes a composite packing scheme utilizing intact rock slabs and broken rock to enhance the thermal energy storage performance of the packed bed. This approach aims to augment heat exchange efficiency and elevate energy storage density while maintaining the bed's commendable permeability. Heat injection and heat extraction experiments of rock beds were conducted to study the heat storage characteristics of the rock-packed bed thermal storage system under different packing structure. In addition, this study investigates the effect of different injection pressures on the storage and release of heat in the system. The results show that the volume of the pore space of the filled bed, serving as the primary domain for gas flow and gas-rock heat exchange, is a decisive factor affecting the packed bed's permeability and heat exchange performance. When the porosity of the packed bed increased from 5.5 % to 9.9 %, its permeability increased from 1.42 × 10−13 m2 to 3.20 × 10−13 m2, yet the thermal exchange efficiency declined from 67.2 % to 65.3 %. Reasonably arranging intact rock slabs and broken rock fill can alter the path of heat transfer within the packed bed, thereby effectively enhancing its heat storage and release performance. For the same pore volume conditions, the heat exchange efficiency of the packed bed is increased by about 10 % by increasing the number of layers of broken rock fill. Additionally, high gas injection pressures can facilitate heat storage and release processes, but it does not mean that this is more efficient. The research findings can guide the selection of packing and injection schemes in packed bed thermal energy storage systems.

ANALYSING THE EFFICIENCY OF USING POROUS METALS IN HEAT EXCHANGERS

This study focuses on analysing the effectiveness of porous metals in heat exchangers, focusing on their effect on improving heat transfer processes. Porous metals, due to their unique structure, have high thermal conductivity and increased contact surface area, which contributes to more efficient heat transfer. As part of the study, experiments and theoretical analyses were carried out to evaluate the effect of porosity coefficient on heat exchange performance. The plotted dependence of Freon mass flow rate and heat quantity on porosity coefficient demonstrate the linear nature of these dependencies. Mathematical processing of the data showed that an increase in the porosity coefficient leads to an increase in both the amount of heat transferred by Freon and Freon mass flow rate, indicating an increase in heat exchange efficiency. The results confirmed that porous metals can significantly improve the performance of heat exchangers and energy saving. Based on the study, further investigation and implementation of porous metals in heat exchangers is recommended to optimise their performance and improve the overall system efficiency. These results open new perspectives for the application of porous metals in various industries including power and mechanical engineering.

Numerical modeling of heat transfer mechanism in remote sensing bulb of thermal expansion valves

Thermal management of automotive systems has garnered a lot of focus in recent times to improve the energy efficiency of vehicles and address the challenge of global warming. In combustible fuel vehicles, the heat pump compressor is driven by the engine power which leads to changes in operating condition of the cycle while the vehicle is in motion. In electric vehicles, a combined thermal management strategy handles both cabin and battery pack cooling/heating depending on the ambient conditions and power requirements by adjusting refrigerant flow rates and flow directions with sophisticated valves. Irrespective of the vehicle type, effective variable refrigerant flow control is prerequisite to ensure optimum thermal comfort with minimum energy. Thermal expansion valves (TXV) are the most widely used method for regulating mass flow rate of refrigerant during the expansion step of the vapor compression cycle based on the principle of trying to maintain a fixed degree of superheat at the evaporator outlet. Conventional models of the thermal expansion valve ignore the time lag between fluctuation of temperature at the evaporator outlet and the corresponding change in pressure of the TXV remote sensing bulb, treating the valve as an instantaneous element during transient operation. This paper presents a novel method for determining the temperature profile and time constant of the remote sensing bulb response using numerical methods, in an attempt to capture the dynamics of thermal expansion valve in active heat pump cycle. Finite difference method was used to solve for the conduction heat transfer between the bulb and the heat exchanger outlet tube in perfect thermal contact applying the necessary boundary conditions. This improved modeling approach will be helpful in better prediction of the dynamic behavior of thermal expansion valves and how it influences the evaporative heat exchanger performance during transient operations to determine control algorithm and strategies.

A multiphysics simulator for stope-coupled heat exchanger operation in deep underground mines

The ever-increasing mine depth offers unprecedented opportunities to access high-grade geothermal resources. By pre-installing pipeline systems in mined-out cavities before waste tailings placement, the stope-coupled heat exchanger (SCHE) has drawn growing attention for its superior socio-economic advantages. However, despite the extensive focus on energy efficiency, the system stability during heat production has been typically overlooked. This study therefore introduces a novel high-fidelity simulator for replicating practical SCHE operation. By embedding non-isothermal pipe flow into an evolutive thermo-poromechanics framework for cemented tailings, the outlet water temperature and multiphysics backfill response in diverse production settings are meticulously studied. Our calculations reveal for the first time that circulating chill fluid within mine backfill can substantially alleviate pressure development, suggesting enhanced system stability with heat-exchanger implementation. We also demonstrate that albeit targeting higher-grade geothermal resources, prioritizing cold-season operation, and pre-charging heat exchangers with production delays could spur heat productivity, the companion thermal pressure generation might still impose significant overloading risks. Conversely, while fast circulation would diminish the end-utilization temperature, the rapid heat removal could indeed facilitate superior efficiency and stability performance for the geothermal system. We believe these new findings hold critical implications for better positioning SCHE as a safely sustainable pathway towards hybrid utilization of deep resources.

Experimental study on the influence factors of falling film heat transfer characteristics outside different types of horizontal tubes

An experimental setup was established to analyze the performance of a spiral wound heat exchanger applied to natural gas liquefaction. The boiling behavior of subcooled flow over a small diameter, non-round, horizontal tube was investigated using n-pentane as the working fluid. The effects of flow rate, heat flux, fluid inlet temperature and tube spacing on heat transfer performance were investigated. Based on the experimental conditions of this study, the results indicate that: (1) raising the Reynolds number can effectively enhance the heat transfer coefficient; (2) the increasing in heat flux also has a positive impact on heat transfer performance, but the extent of which is related to the Reynolds number; (3) increasing the tube spacing resulted in higher heat transfer coefficients; (4) under the same working conditions, the heat transfer performance of non-round tubes is higher than that of round tubes; (5) correlation equations were developed to calculate the Nu for smooth, round, elliptical, and egg-shaped tubes. The predictions made by these correlation equations deviated by less than 10 % from the experimental results for the entirety of the experimental conditions.

Novel 2D Layered MXene Nanofluids for Enhancing the Convective Heat Transfer Performance of Double-Pipe Heat Exchangers.

This paper proposes a new class of novel 2D layered structured materials, such as MXene (MX), for the synthesis of innovative nanofluids as coolants to evaluate the convective heat transfer performance of a double-pipe heat exchanger (DPHE). Convective heat transfer experiments were successfully conducted in lab-scale fabricated DPHE using low-concentration MXene nanofluids by varying the volume concentration of MXene nanoparticles (0.01-0.05 vol %) in different base fluids. The influence of the MXene nanofluids on various convective heat transfer parameters, such as LMTD, Nusselt number, heat transfer coefficient, and heat transfer rate without using any inserts in the DPHE was experimentally investigated. The results of the experiments revealed that the heat transfer coefficient and Nusselt number increase with increasing Reynolds number (Re) and concentration of MXene nanoparticles in the base fluids. Maximum enhancement in heat transfer coefficient (126%) was achieved for methanol-based MXene nanofluids at 0.05 vol %. Moreover, the Nusselt number exhibits a maximum enhancement of ∼50% for methanol- and water-based MXene nanofluids. In contrast, the thermal performance factor was also estimated, and it was observed that water- and methanol- based MXene nanofluids showed higher values than castor oil- and silicone oil-based MXene nanofluids. Finally, the LMTD and heat transfer coefficients were successfully validated using Aspen HYSYS 12.1 software.

Performance analysis of a solar-assisted ground source heat pump with a single vertical U-tube ground heat exchanger

Owing to higher heat loads than cooling loads in cold climates, the performance of ground source heat pumps (GSHPs) can significantly degrade over time, leading to eventual system failure for systems not properly sized or when there is insufficient regeneration. Solar-assisted ground source heat pump (SAGSHP) systems are receiving increasing interest as a means of enhancing heating performance and maintaining ground thermal balance in cold regions. However, a critical gap remains in the literature: no study has comprehensively analyzed configurations of SAGSHP systems to enhance their overall performance considering long-term performance and realistic operating conditions. For this purpose, a comprehensive investigation of the long-term performance of single U-tube and double U-tube ground heat exchangers (GHEs) for solar-assisted ground source heat pump systems (SAGSHPs) was carried out and compared with the conventional GSHP. The effect of collector tilt angles (0–90°) on the performance of the single U-tube SAGSHP was also examined. A finite volume computational fluid dynamic model was developed and coupled with an actual building energy load profile and a solar irradiation profile based on Calgary’s weather conditions using a novel custom-coded thermodynamic model. Results show that the yearly average heating coefficient of performance (COP) increases by a factor of 1.21 and 1.18 for the single U-tube SAGSHP and double U-tube SAGSHP, respectively, when compared with the conventional GSHP. However, the average annual cooling COP reduces by 0.65 for the single U-tube and 0.72 for the double U-tube SAGSHPs. Moreover, considering the effect of tilt angle on the single U-tube SAGSHP, it is possible to improve the cooling COP when the collector tilt angle is 90°, at the expense of lower heating COP. However, the highest heating COP and annual energy savings are achieved with a tilt angle of 45°. This study provides practical insight into SAGSHP performance enhancements in cold climates.

Improvement in heat transfer and flow pattern of sprayed falling on horizontal tubes with rib structure for a sewage source heat pump

The falling film flow and heat transfer characteristics are critical to improve the performance of spray heat exchangers in a sewage source heat pump (SSHP), which is influenced by the operating and structural parameters. Therefore, considering the unique flow patterns of wastewater falling film caused by the oily content, and the influence of heat exchange tubes with surface structures on flow and heat transfer, two types of heat exchanger tubes with axial and circumferential ribs were designed and the falling flow over tubes were investigated through CFD method using VOF model. The falling film flow pattern, liquid film coverage and heat transfer coefficient (HTC) outside the ribbed heat exchange tubes were investigated, and the influence of rib structures and Re were analyzed. It was found that oily wastewater liquid film spreaded differently depending on the rib structures, and circumferential ribs of case 2 improved the flow pattern by increasing film coverage, which obviously affected the tube HTC. At higher Re, the ribbed tubes displayed higher potential in better heat transfer performance. Therein, the circumferential ribbed tubes showed highest average HTC, with up to 31.9 % higher than smooth tubes, which can be further enhanced by increasing Re. This study provides a foundation for enhancing the heat transfer performance of spray heat exchangers in sewage source heat pumps through the design and modification of tube surface structures.