Frictional Pressure Research Articles

Water Distribution Challenges in Northeast Trinidad and Tobago

Provision of a reliable supply of water with adequate pressures is a paramount challenge for the water distribution network in Northeast Trinidad and Tobago. Customers in this region, served by the Water and Sewerage Authority of Trinidad and Tobago experience difficulties in obtaining a pipe borne supply of water as they reside on areas of high elevation or are at the farthest end of the distribution system. Areas where water supply challenges are a problem are Oropoune Gardens Piarco, Upper Five Rivers Arouca, Windy Hill Arouca, Edna Hill Arouca, Lillian Heights Arouca, The Foothills Arouca, Pineridge Heights Housing Development and Ridgeview Heights Housing Development Bon Air North. Sources of supply to these impacted areas are the North Oropouche Water Treatment Plant, the Hollis Water Treatment Plant, the Tacarigua High Lift Station and Arouca wells. Challenges in the water supply are a consequence of obsolete pipelines, numerous leaks, failure of mechanical equipment and a shortened duration of supply. This paper identifies the inefficiencies and challenges of the water distribution system in this region by simulating flow through crucial transmission and distribution pipelines using ANSYS Fluent simulation. The Hazen-Williams equation was used to calculate frictional pressure loss in the respective crucial pipelines. Using the results from both analyses, prospective solutions to alleviate and eliminate the inadequate water supply experiences faced by customers in these areas were advocated.

Experimental insights into energy savings and future directions of drag reducing polymers in multiphase flow pipelines

Frictional pressure drop has been grasping the attention of many industrial applications associated with multi-phase and academia. Alongside the United Nations, the 2030 Agenda for Sustainable Development calls for the exigency of giving attention to economic growth, a considerable reduction in power consumption is necessary to co-up with this vision and to adhere to energy-efficient practices. Thereinto, drag-reducing polymers (DRPs), which do not require additional infrastructure, are a much better option for increasing energy efficiency in a series of critical industrial applications. Therefore, this study evaluates the effects of two DRPs—polar water-soluble polyacrylamide (DRP-WS) and nonpolar oil-soluble polyisobutylene (DRP-OS)—on energy efficiency for single-phase water and oil flows, two-phase air–water and air-oil flows, and three-phase air–oil–water flow. The experiments were conducted using two different pipelines; horizontal polyvinyl chloride with an inner diameter of 22.5 mm and horizontal stainless steel with a 10.16 mm internal diameter. The energy-efficiency metrics are performed by investigating the head loss, percentage saving in energy consumption (both per unit pipe length), and throughput improvement percentage (%TI). The larger pipe diameter was used in experiments for both DRPs, and it was discovered that despite the type of flow or variations in liquid and air flow rates, there was a reduction in head loss, an increase in energy savings, and an increase in the throughput improvement percentage. In particular, DRP-WS is found to be more promising as an energy saver and the consequent savings in the infrastructure cost. Hence, equivalent experiments of DRP-WS in two-phase air–water flow using a smaller pipe diameter show that the head loss drastically increases. However, the percentage saving in power consumption and throughput improvement percentage is significantly compared with that found in the larger pipe. Thus, this study found that DRPs can improve energy efficiency in various industrial applications, with DRP-WS being particularly promising as an energy saver. However, the effectiveness of these polymers may vary depending on the flow type and pipe diameter.

Condensation of R290 + R13I1 zeotropic mixture in a plate heat exchanger with offset-strip fin geometry

Energy-efficient refrigerants with a low global-warming potential (GWP) is becoming increasingly popular, particularly in the automobile sector. In this sense, despite its higher flammability, R290 can meet environmental regulations with outstanding thermal properties. Studies have been conducted to reduce the flammability of R290 by combining it with flame retarding agents, and it has been discovered that the use of R13I1 has good control over R290's flammability and offering good thermal performance. However, research into the two-phase behavior of R290 + R13I1 combinations is extremely important for building compact heat-pumps. Therefore, this study experimentally investigated the condensation behavior of a new low-GWP R290 + R13I1 refrigerant mixture in a plate heat exchanger with an offset-strip fin flow passage. The effects of the heat flux (HF), mean vapor quality (xm), saturation temperature (Ts), and mass flux (MF) on the condensation heat transfer coefficient (HTC) and two-phase frictional pressure drop were explored. The results show that the peak condensation HTC increased by 66.2% and 19.7% with an increase in HF and MF, respectively, although it deteriorated by 26.7% in the case of Ts. Moreover, the dominance of the mass transfer resistance (MTR) and surface tension was observed at lower xm values, whereas the shear force dominated at higher xm values. The MTR was estimated with Silver–Bell–Ghaly (SBG) approximation, and the values were in the range of 0.0000342 K.m−2.W−1 and 0.000067 K.m−2.W−1. Moreover, the Nusselt number (Nu) predicted using the SBG approximation correlations was lower than the experimental value. Hence, two types of new Nu correlation were made with and without SBG approximation, and they showed reasonably good Nu prediction with 9.6% and 10.8% mean absolute deviation.

Corrigendum to “A discussion on the relation between the intermittent flow sub-regimes and the frictional pressure drop” [Int. J. Heat Mass Transf. 181 (2021) 121895

The influence of sub-regimes of intermittent flow on the pressure drop has been investigated. Two-phase, air-water, flow experiments were conducted on 30 mm ID pipe. The superficial velocities of the working fluids were chosen to cover three sub-regimes: Plug flow, Less Aerated Slug flow (LAS flow) and Highly Aerated Slug flow (HAS flow). The analysis of the experimental data, including the data drawn from the literature showed that the pressure drop depends on the flow sub-regime. A new empirical correlation, based on the Lockhart-Martinelli approach, taking into account the nature of sub-regime was proposed. The present correlations, in comparison with the existing correlations, give the best results.

Experimental study on sub-regimes of air-water slug flow in a rectangular micro-channel

In mini/micro-channel two-phase flow, slug flow occurs easily because of the significant influence of surface tension and the low gravitational effect on the flow. Although an irregularity of slug flow has been reported, previous studies on mini/micro-channel slug flow have mainly concerned the slug flow with the alternate of film and liquid slug zones regularly. Therefore, the present study investigates sub-regimes of micro-channel slug flow with regular or irregular alternating film and liquid slug zones to understand their principal characteristics. Experiments are performed to visualize and simultaneously measure the transient local pressure of the air-water mixture flow in a horizontal rectangular channel with a 2 mm height and 1 mm width. Superficial Reynolds numbers for liquid and gas phases range from 56 to 1116 and 5.75 to 245, respectively. With the aid of visualization data, slug flow is categorized into two types of stable slug flow and four types of unstable slug flow. Present slug flow data is compared with previous correlations for predicting the regime of bubble formation mechanism, flow regime boundaries, and frictional pressure gradient. Measured temporal pressure records are analyzed using a fast Fourier transform and digital Butterworth filter, while a dominant frequency is identified from the normalized average power spectrum. Then, the local pressure fluctuation at the dominant frequency is examined for different types of slug flow using the visualization results. A morphological repetition is confirmed to be associated with the pressure fluctuation: the repeated film and liquid slug zones in both types of stable slug flow, the alternative between liquid-only flow and a group of gas bubbles and liquid slugs in type 3 unstable slug flow, and the periodic variation of bubble length in type 4 unstable slug flow. However, no correlation between morphological characteristics and pressure fluctuation is found in type 1 and 2 unstable slug flows.

The influence of flow pattern and hopper angle on static and dynamic pressures in slender silos

This paper focuses on the influence of flow pattern and hopper angle (β) on static and dynamic pressures in slender silos. The results were obtained using a test station developed by the authors, consisting of a silo (6 m high and 0.7 m internal diameter). Maize was used to generate the pressures. Five different hopper angles were tested by filling, static phase followed by complete silo discharge. Results are reported for pressure and flow analyses, and show that hopper angle influences normal pressures on the silo wall; Silos with transition flow do not have a concrete pattern of distribution of thrusts; pressure values are proportional to the variation of the hopper angle; and internal shear zones vary according to hopper angle, completely modifying the behaviour of static and dynamic pressures. Friction pressure and lateral pressure ratio values exceeded those calculated by the Eurocode 1, part 4.

Experimental investigation on the condensation of R32 flowing inside alternating cross-section flattened tubes with different aspect ratios

In this experiment, we investigated the condensation of R32 flowing inside alternating cross-section flattened (ACF) tubes with various aspect ratios. ACF tubes were made from a copper circular tube with a 4.31-mm inner diameter. Three ACF tubes with aspect ratios of 5.82 (ACF1), 4.11 (ACF2), and 3.23 (ACF3) were used as test tubes. The experimental conditions covered a mass flux of 280–580 kg/m2s, a heat flux of 10–20 kW/m2, a saturation temperature of 40 °C, and a vapor quality of 0.1–0.8. The results revealed that most experimental data fell into the annular flow regime when using existing flow patterns. In comparison, the ACF1 tube obtained the highest heat transfer coefficient (HTC) and pressure drop (ΔP). The HTC of ACF tubes outperformed those of the circular tube by about 1.7–6.9 (for ACF1), 1.1–2.8 (for ACF2), and 1.2–2.1 (for ACF3) times. In addition, ACF tubes provided a greater frictional pressure drop than circular tubes, around 1.0–2.3 (for ACF1), 1.2–1.9 (for ACF2), and 1.0–1.4 (for ACF3) times. However, the ACF1 achieved the best overall performance by approximately 2.1 times, superior to the circular tube. Since the existing correlations failed to predict the Nusselt number and two-phase friction factor, we propose new correlations for the ACF tube with mean deviations of 14.9% and 7.3%, respectively.

Thermal-hydraulic performance enhancement of fin-and-tube heat exchangers using carbon nanotube coatings under dry and wet conditions

Carbon nanotube coatings have been widely adopted in various heat transfer fields to improve their heat transfer performance. However, comprehensive studies on the thermal–hydraulic performance of fin-and-tube heat exchangers with carbon nanotube coatings are limited. In this study, the heat transfer characteristics of fin-and-tube heat exchangers with uncoated, hydrophilic, hydrophobic, and carbon nanotube coatings were measured under dry and wet conditions. The Colburn j-factor, friction factor, and thermal–hydraulic performance (jf–1/3) of fin-and-tube heat exchangers with various coatings were analyzed and compared under dry and wet conditions. The carbon nanotube-coated heat exchanger showed the best performance in terms of heat transfer and frictional pressure drop under both dry and wet conditions among the tested fin-and-tube heat exchangers. This is because the unique microscopic surface structure of the carbon nanotube coating increased the heat transfer coefficient, whereas the superlubricity of the carbon nanotube coating decreased the frictional pressure drop. The behavior of liquid droplets on the surfaces of various fin-and-tube heat exchangers was investigated in detail under dry and wet conditions. In addition, the thermal–hydraulic performance (jf–1/3) of the carbon nanotube-coated heat exchangers was 8.9% and 6.1% on average higher than that of the uncoated heat exchanger under dry and wet conditions, respectively. The results of this study can provide helpful information for developing fin-and-tube heat exchangers with carbon nanotube coatings to achieve substantial energy savings.

Experimental study on friction pressure drop and circumferential heat transfer characteristics in helical tubes

Helical tubes are widely used in nuclear plants, heat recovery process, and refrigeration technology. The fluid is influenced by centrifugal force flow through the helical tube, accompanied by secondary flow which is conducive to the enhancement of heat transfer. However, the uneven circumferential heat transfer caused by the secondary flow was seldom reported, while the pressure drops and heat transfer characteristics of helical tubes under single-phase and two-phase flow conditions need to be supplemented. This paper investigated the friction pressure drop and circumferential heat transfer characteristics based on the experiments on helical tubes with the coil diameter to the tube diameter varying from 28.5 to 128.5 and lift angle varying from 3° to 10°. The results showed that the coil diameter was the key parameter affecting the pressure drop and non-uniform circumferential heat transfer, compared with the lift angle. At the same cross section, the heat transfer coefficient at the outside tube wall was the highest, which was more obvious under small coil diameter conditions. Correlations of flow resistance and heat transfer were proposed for the single-phase and saturated boiling two-phase flow, respectively, and the predicted values were improved compared with the prediction results of correlations in the existing literature.

An Experimental Investigation of Two-Phase Frictional Pressure Drop in Straight-Tube Steam Generator Used in SFR

Due to the presence of sodium, it is a challenging task to achieve the reliable and safe operation of steam generators in a sodium-cooled fast reactor (SFR). Water flow oscillations in a two-phase flow system worsen the tube integrity. An accurate prediction of two-phase pressure drop is essential in designing steam generators to operate in a stable regime. Toward this, experiments have been carried out on an industrial-size 19-tube model sodium-heated steam generator of 5.5-MW capacity to understand two-phase pressure drop characteristics at various operating conditions. The measured data are used to estimate the two-phase frictional pressure drop. The concept of a two-phase friction multiplier has been used in the present study. A significant variation in the two-phase frictional multiplier is seen with steam quality, whereas the variation of the two-phase friction multiplier is insignificant at saturated steam condition. Based on the experiments, complemented by computational model, a correlation has been developed for the two-phase frictional multiplier as a function of steam quality for sodium-heated once-through straight-tube steam generators.

CFD-Based Approach to Propose a Zigzag-Shaped Tube Heat Exchanger without Fins

This study explores the application of zigzag-shaped, finless tubes in enhancing heat transfer performance within heat exchangers. Using three-dimensional numerical simulations, we examined the heat transfer per unit area and the volume of the pressure drop, comparing these findings with a traditional parallel tube heat exchanger. This innovative design strategy involved arranging zigzag-shaped tubes at varying distances, and the thermal transfer and frictional characteristics were tested at different air speeds. This research suggests that the introduction of zigzag heat exchangers, as opposed to traditional fin-and-tube designs, led to a significant improvement in heat transfer. This enhancement is attributed to the swirling flow created around the zigzag tubes, which increased the total heat transfer area. Furthermore, we found that the heat transfer area increased by 14.2%, 32.1%, and 63.9% for tube zigzag angles of 30°, 45°, and 60°, respectively, when compared to a parallel tube heat exchanger. Consequently, the zigzag-shaped tube heat exchanger demonstrated not only superior heat transfer, but also a reduction in frictional pressure loss.

Use of artificial neural networks in the prediction of horizontal and friction pressures in a slender silo

Structural reliability studies in silo pressure predictions are a subject of great interest because the number of variables in silo pressure calculations is large, which can generate numerous failures and occurrences of collapse. The objective of this study was to propose a pressure prediction model using artificial neural networks (ANNs) in comparison with experimental data. For data collection, a pilot silo model, proposed by Pieper and Schutz (1980), adopted by the German standard DIN 1055 (1987), was used. The pressure measurements were performed during loading and unloading of the silo. Smooth walls with flat bottom were used in the silo, varying the height/diameter ratio between 4, 6 and 8. The pressures observed on the silo walls were the horizontal pressures and the friction pressure of the product with the wall. The results of the pressures obtained experimentally were fed into an algorithm using multilayer Perceptron ANNs. The pressures measured on the silo walls were compared with the values predicted by ANNs, linear and polynomial regressions, and also with the values calculated by means of the European Standard EN 1991-4: 2006 and Australian Standard AS 3774 (1996). Among the models used, the best performance was obtained by ANNs, which were able to predict silo wall pressures with smaller errors.

Modelling of flow in backward erosion pipes

Backward erosion piping is an important failure mechanism that can affect the safety of water-retaining structure foundations, which results in the formation of shallow pipes at the interface of the cohesive layer and the sand layer. Pipe hydraulics provides a lot of valuable information about the erosion mechanism, but it had never been analysed systematically during equilibrium. This paper analyzes pipe hydraulics by combining the pipe flow model and numerical simulations of experiments. A single-phase pipe-flow model is presented that includes not only frictional and accelerational pressure drops, but also the pressure drop caused by inflow through the pipe wall. The pipe-flow model is included in pipe/aquifer coupling numerical models to achieve more accurate predictions of pressure drop and inflow distribution along the pipe. The predictions agree favourably with previously published experimental data. And the calculated pipe flow velocities, hydraulic regimes and gradients are analysed for different pipe lengths.

Method for calculating pressure losses in the pipelines of slurry shield tunneling based on coupled simulation of computational fluid dynamics and discrete element method

AbstractHydraulic mucking/transport or slurry pipelining are widely used in dredging, trenching, (deep sea) mining, tunnel boring, and many other applications. Slurry pipelining during slurry shield tunneling is a classic instance of complex hydraulic mucking systems, which is characterized by the complex rheological behavior of the slurry and the inclusion of large and irregular particles. These characteristics make it difficult to estimate the pressure losses along slurry pipelines, compared to other hydraulic mucking systems. This study established a powerful method for predicting the pressure losses in long‐distance slurry pipelining of slurry shield tunneling based on computational fluid dynamics–discrete element method (CFD‐DEM)‐coupled simulations. Rheological tests were carried out to provide reliable slurry flow parameters for CFD calculations. Irregular pebbles with different sizes were digitally scanned using 3D scanning technology, and the scanned models were applied to the DEM. This method was successfully applied to a slurry shield tunnel project in Beijing, China. The mechanical properties of the fluid phase and particle phase were revealed by modeling a typical slurry pipeline. A comparison of the pressure losses along slurry pipelines was made between the proposed method and field data, indicating the validity of the established method. The simulation results indicate that when the slurry flows through the elbow, a secondary flow will be formed due to centrifugal force. Pebbles of different sizes show different motion responses under the combined action of gravity and slurry coupling force. The turbulent flow of particles will increase the frictional pressure losses in the elbow area, compared to the straight section. This work provides a valuable reference for the layout of the slurry circulation system of similar projects.

Evaluation of prediction models on frictional pressure drop for condensation flow in horizontal circular tubes

ABSTRACT There are numerous correlations available for predicting frictional pressure drop of condensing flow in horizontal tubes. It is necessary to evaluate and analyze the prediction accuracy and applicability of existing correlations. In order to explore the versatility of frictional pressure drop correlations for condensation flow with different working fluids, four existing models are investigated: phase-separation conversion model, full-phase flow model, two-phase multiplier flow model, and homogeneous flow model. Combined with five different working fluids (R170, R12, R600a, R22, R1234yf), 402 groups of experimental data on frictional pressure drop for condensation flow in horizontal circular tubes are considered with respect to flow pattern. The prediction results based on each correlation are compared and analyzed. Mean absolute relative deviation (MARD) and mean relative deviation (MRD) are selected as indicators to evaluate each correlation. The results showed that the versatility of the existing correlations needs improvement. The prediction accuracy of frictional pressure drop for condensation flow can be improved by selecting different correlations for different flow patterns. The phase-separation conversion model has a good prediction effect and a wide application scope in annular flow. The maximum MARD is 15.85%, and the maximum MRD is 8.72%. 93.08% of the data predicted deviation is less than 30%. This study will provide some constructive instructions to predict frictional pressure drop of condensation flow in horizontal circular tubes for designing heat exchangers.

Comprehensive modeling of frictional pressure drop during carbon dioxide two-phase flow inside channels using intelligent and conventional methods

Environmentally friendly nature of CO2, associated with its safety and high efficiency, has made it a widely used working fluid in heat exchangers. Since CO2 has strange thermophysical features, specific models are required to estimate its two-phase characteristics, particularly frictional pressure drop (FPD). Herein, a widespread dataset, comprising 1195 experimental samples for two-phase FPD of CO2 was adopted from 10 sources to fulfill this requirement. The literature correlations failed to provide satisfactory precisions and exhibited the average absolute relative errors (AAREs) between 29.29% and 67.69% from the analyzed data. By inspiring the theoretical method of Lockhart and Martinelli, three intelligent FPD models were presented, among which the Gaussian process regression approach surpassed the others with AARE and R2 values of 5.48% and 98.80%, respectively in the test stage. A novel simple correlation was also derived based on the least square fitting method, which yielded opportune predictions with AARE of 19.76% for all data. The truthfulness of the newly proposed models was assessed through a variety of statistical and visual analyses, and the results affirmed their high reliability over a broad range of conditions, channel sizes and flow patterns. Furthermore, the novel models performed favorably in describing the physical attitudes corresponding to two-phase FPD of CO2. Eventually, the importance of operating factors in controlling the FPD was discussed through a sensitivity analysis.

Experimental investigations of the flow boiling characteristics of green refrigerants in a novel petaloid micropin-fin heat sink

Although micropin-fin heat sinks (MPFHSs) are widely regarded as an effective way to dissipate heat in microelectronic equipment, the pin fin structure has not changed much over the years. Inspired by the flower of Clematis montana, a novel petaloid structure was designed. The flow boiling characteristics of green refrigerants, including R1234ze(E) and R1234yf, in the petaloid MPFHS were investigated under mass fluxes of 100–200 kg/m2 s, heat fluxes of 20–40 kW/m2 and saturation pressures of 0.4–0.6 MPa and compared with those of R134a. In the nucleate boiling zone, the heat transfer coefficient (HTC) rises with saturation pressure, vapor quality, and heat flux; in the convective boiling region, it rises with mass flux. With mass flux and vapor quality, the frictional pressure drop (FPD) rises; with saturation pressure, it falls; with heat flux, it keeps constant. R1234ze(E) shows the largest HTC and the smallest FPD, and R1234yf and R134a have similar HTC and FPD. Specific bubbles, slugs, confined slugs and liquid films yielded by the petaloid micropin fins are identified, and the flow behaviors, including coalescence and separation of bubbles/slugs, are described. Comparing the existing empirical correlations for flow boiling HTC and FPD in plain and micropin-fin channels with the experimental data yields unsatisfactory mean absolute deviations (MADs). Hence, new correlations for petaloid MPFHS are developed, which yield satisfactory MADs of 12.6% and 9.9% for HTC and FPD, respectively.

Experimental study of swirling flow pneumatic liquid-carrying characteristics in the vortex tool inserted tube under liquid loading conditions

Liquid unloading by vortex tool is one of the most important applications of swirling flow pneumatic conveying. However, due to swirl decay, the evolution of gas–liquid flow patterns and the dynamic characteristics of pressure drop downstream of the vortex tool are much more complex than those in non-swirling flow. In this study, the gas–liquid flow patterns and pressure drop inside the vortex tool inserted tube (ID = 60 mm) under liquid loading conditions were experimentally studied and compared with those of the plain tube. With the superficial gas velocities ranging from 0.5 to 6.0 m/s and superficial liquid velocities of 0.01, 0.02, and 0.04 m/s, the effects of the structural parameters and stages of vortex tools on the pressure drop were discussed. The experimental results reveal that three distinct swirling flow patterns can be identified downstream of the vortex tool, namely swirling gas column flow, swirling churn flow and swirling annular flow. The insertion of vortex tool facilitates an earlier transition of the churn flow to the annular flow, and the induced swirling flow can restrain the liquid from falling back. The helix angle of the corkscrew deflector has a more significant effect on the pressure drop than its length. By reducing the helix angle from 54° to 45°, the total pressure drop and downstream pressure gradient are significantly decreased, even lower than those of the plain tube. But the series combination of 54° and 45° vortex tools results in a significant increase in the downstream pressure gradient. Additionally, at low gas flow rate, negative frictional pressure drop occurs in both plain tube and vortex tool inserted tube. Hence, the new friction factor correlations were established respectively for the positive and negative friction regions in the cases of the tube with and without vortex tool, and most of the frictional pressure gradient predictions are within an error band less than 20%.

Effect of friction pressure on microstructure and tensile properties of linear friction welded Ti–6Al–4V alloy joints

This investigation aims to study the influence of friction pressure (FRNP) on the evolution of microstructure and tensile properties of Ti6Al4V alloy joints developed using linear friction welding (LFW) for aeroengine applications. The Ti6Al4V alloy plates of 6 mm thickness were joined using different levels of FRNP from 10 MPa to 30 MPa. The weld joint quality was analyzed employing stereo-zoom microscope. The microstructure of LFW joints was studied using optical (OM), scanning electron (SEM) and transmission electron microscope (TEM). The hardness and tensile properties were evaluated and correlated to the microstructure of joints. The fractographs were studied using SEM and correlated to the hardness. The LF welded Ti6Al4V joints made using the optimum level of FRNP of 20 MPa exhibited greater tensile strength (UTS) of 993 MPa, and elongation (EL) of 8%. It showed notch tensile strength (NTS) of 1073 MPa and notch strength ratio (NSR) of 1.041 revealing ductile fracture. The LF welded Ti6Al4V joints revealed 96.41%, 104.10% and 66.67% of UTS, NTS and EL of base metal. The greater smooth and notch tensile properties of joints are principally imputed to maximum refinement of alpha + beta grains at interface of joint.

Study on anti-wear and friction-reducing compounding additives in lithium greases

PurposeThis paper aims to determine a suitable anti-wear and friction-reducing compounding additive for lithium greases (LG) by investigating the effects of three single additives potassium borate (PB), zinc dialkyl dithiophosphate and molybdenum dialkyl dithiophosphate (MoDDP) and two compound additives on the friction, wear and extreme pressure properties of LG.Design/methodology/approachThe effects of the above five additives on the friction, wear and extreme pressure properties of LG were investigated using an SRV-5 friction tester. An X-ray photoelectron spectrometer was used to analyze the various elements presented on the wear surface as well as the types of compounds.FindingsThe compound additive suitable for grease consists of PB and MoDDP, which have excellent friction reduction, anti-wear and extreme pressure properties. And a boundary protection film consisting of oxide and MoS2 is formed on the friction surface, thus improving the friction reduction and anti-wear performance of the grease.Originality/valueThis study can improve the anti-wear and friction-reduction performance of greases, which is of great importance in the field of industrial lubrication. The results of this paper are expected to be useful to researchers and academics of grease.Peer reviewThe peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-11-2022-0350/