Thermal Dissipation Research Articles

Performance prediction of ventilated building-integrated photovoltaic system with lightweight flexible crystalline silicon module based on experimental fitting method

The novel ventilated building-integrated photovoltaic system with lightweight flexible crystalline silicon modules (VL-BIPV) has a self-weight of only about 6 kg/m2, which helps to address weight-bearing challenges on low-capacity industrial building rooftops. However, the unique thermal dissipation features of the system pose challenges for the analysis of its photovoltaic performance and thermal processes. Therefore, a comparative experimental testing approach was employed, comparing the VL-BIPV system with a conventional rooftop photovoltaic system. Using the efficiency equations of the conventional photovoltaic system as a reference, the functional equations were fitted based on experimental results. Based on typical meteorological year data in Nanjing, annual power generation and PV cell temperature variations were evaluated, along with power generation and carbon reduction benefits over a 25-year lifetime. The results indicate that the VL-BIPV system achieves an annual power generation of 262.22 kWh/m2, a 6.52% increase compared to the conventional system. Additionally, the highest average and maximum cell temperatures in the VL-BIPV system during the year are 58.39 °C and 64.74 °C, respectively, both lower than the conventional system's peak at 68.34 °C. Over a 25-year lifespan, the VL-BIPV system reduces carbon emissions by 20.17 kgCO2/Wp, exceeding the conventional system's reduction by 1.25 kgCO2/Wp.

Thermophysical Profile of Industrial Graphene Water-Based Nanofluids.

The exceptional properties of high-grade graphene make it an ideal candidate for thermal dissipation and heat exchange in energy applications and nanofluid development. Here, we present a comprehensive study of few-layer graphene (FLG) nanofluids prepared in an industrial context. FLG nanofluids were synthesized through an ultrasound-assisted mechanical exfoliation process of graphite in water with a green solvent. This method produces FLG of high structural quality and stable nanofluids, as demonstrated by electron microscope, dynamic light scattering and ζeta potential analyses. Thermal conductivity measurements of FLG-based nanofluids were conducted in the temperature range of 283.15 K to 313.15 K, with FLG concentrations ranging from 0.005 to 0.200% in wt. The thermal conductivity of FLG nanofluids is up to 20% higher than water. The modeling of nanofluid thermal conductivity reveals that this enhancement is supported by the influence of the thermal resistance at the FLG interface, and the content, average dimensions and flatness of FLG sheets; this latter varying with the FLG concentration in the nanofluid. Additionally, the density and heat capacity of FLG suspensions were measured and compared with theoretical models, and the rheological behavior of FLG nanofluids was evaluated. This behavior is mainly Newtonian, with a weak 5% viscosity increase.

Topological Anderson phases in heat transport

Topological Anderson phases (TAPs) offer intriguing transitions from ordered to disordered systems in photonics and acoustics. However, achieving these transitions often involves cumbersome structural modifications to introduce disorders in parameters, leading to limitations in flexible tuning of topological properties and real-space control of TAPs. Here, we exploit disordered convective perturbations in a fixed heat transport system. Continuously tunable disorder-topology interactions are enabled in thermal dissipation through irregular convective lattices. In the presence of a weak convective disorder, the trivial diffusive system undergos TAP transition, characterized by the emergence of topologically protected corner modes. Further increasing the strength of convective perturbations, a second phase transition occurs converting from TAP to Anderson phase. Our work elucidates the pivotal role of disorders in topological heat transport and provides a novel recipe for manipulating thermal behaviors in diverse topological platforms.

Thermal Management and Optimization of Automotive Film Capacitors based on Parallel Microchannel Cooling Plates

Abstract The automotive film capacitors (AFCs) stand as a widely employed components in electric vehicles. Yet, a notable concern arises with the potential for excessive ripple current, which can prompt self-heating in the AFC and diminish its reliability. Therefore, it becomes crucial to conduct thermal management and effective heat dissipation design for the AFC to ensure its optimal performance. In this study, considering the trend toward integrated and lightweight motor controllers, a parallel microchannel cooling plate (PMCP) is designed at the bottom of the AFC. Through optimization, the thermal performance of the AFC and the overall cooling performance of the PMCP are enhanced. The AFC thermal model is established and the calculation method for equivalent thermal properties of the film capacitor core is described. A conjugate heat transfer simulation model for the AFC and the PMCP is created by FLUENT and validated through two experimental tests. Additionally, based on an optimal Latin Hypercube Sample size, the accuracy of five fitting models is compared and the non-dominated sorting genetic algorithm II (NSGA-II) for optimization is employed. The results indicate that the error between the simulation method and the two experiments is within 5 %. The application of the PMCP effectively redistributes the hottest region of the AFC to the outer housing, reducing the maximum AFC temperature by 10.90 °C. Among the five fitting models, the RSM (Response Surface Model) proved to be the most accurate. The optimized PMCP enhances the overall cooling performance by 10.32 %, and increases the maximum withstand ripple current of the AFC by 43.83 %.

Enhancing triboelectrification via multiscale roughness dependent thermal dissipation

Polymer-based triboelectric nanogenerators (TENGs) have held promise due to their excellent interfacial conformity and ease of fabrication. However, the role of surface roughness in triboelectricity requires further study. In this study, we have manipulated the nano-/micro-scale roughness configuration in polydimethylsiloxane (PDMS) over a wide range of extents using various sandpaper-based templates. According to the power spectral density analysis, the spatial frequency of template-free PDMS exhibits several distinct bandwidth regions each with different fractal dimensions significantly higher than 2, despite having the lowest roughness value. In contrast, most template-based PDMS shows an entire spatial frequency region that scales nearly with a single power factor corresponding to a fractal dimension as low as 2, despite slight increases in roughness values. Consequently, the surface temperature gradient and output performance of TENG increased, following the trend of fractal dimension and roughness, but the surface potentials have remained almost invariant. However, excessive increases in the surface roughness cause the spatial frequency to be divided once again into several different bandwidth regions with different cutoffs and higher fractal dimensions. These results suggest that the performance of TENG can be controlled by tuning both surface roughness and self-affine properties over multiple scales. Specifically, adhesive interaction becomes dominant on surfaces with lower fractality, enhancing TENG performance due to the expanded contact area. This study sheds light on the relationship among triboelectricity, thermal dissipation, and topography.

Numerical study on heat dissipation of double layer enhanced liquid cooling plate for lithium battery module

The thermal management system's architecture is crucial for lithium batteries' efficiency and financial viability, predominantly influencing their security and longevity. We conceptualized a double-layer enhanced LCP, meticulously crafted to augment the heat dissipation capabilities of the battery assembly. This novel design targets the reduction of peak temperatures and pressure drops, fostering an even internal temperature profile. Comprehensively evaluate the performance of different settings of the coolant cooling system, and the monitoring points are strategically set in horizontal and vertical directions. Analyzing the data, it becomes evident that the system's vertical orientation significantly affects the battery module's peak temperature and temperature variation. Furthermore, extensive investigations were conducted on the impact of layout, coolant flow rate, and inlet temperature on thermal dissipation. Our findings indicate that the double-layer enhanced liquid cooling plates outperform conventional designs. There is a substantial 2.41 % decrease in the peak battery module temperature and an 80.6 % reduction in voltage decline. Operating at a flow rate of 10 g per second and an entry temperature of 25 °C, our liquid cooling system demonstrates superior cooling efficiency with minimal power consumption. It proficiently restrains the maximum battery module temperature below 30.43 °C and restricts temperature variance to merely 3.48 °C. The suggested approach in this research contributes to improved thermal equilibrium, diminishes temperature disparities and pressure concerns, thereby fostering the technological advancement of electric vehicle's liquid cooling systems.

Durable and programmable ultrafast nanophotonic matrix of spectral pixels.

Locally addressable nanophotonic devices are essential for modern applications such as light detection, optical imaging, beam steering and displays. Despite recent advances, a versatile solution with a high-speed tuning rate, long-life durability and programmability across multiple pixels remains elusive. Here we introduce a programmable nanophotonic matrix consisting of vanadium dioxide (VO2) cavities on pixelated microheaters that meets all these requirements. The indirect Joule heating of these VO2 cavities can result in pronounced spectral modulation with colour changes and ensures exceptional endurance even after a million switching cycles. Precise control over the thermal dissipation power through a SiO2 layer of an optimized thickness on Si facilitates an ultrafast modulation rate exceeding 70 kHz. We demonstrated a video-rate nanophotonic colour display by electrically addressing a matrix of 12 × 12 pixels. Furthermore, inspired by the unique pixel-level programmability with multiple intermediate states of the spectral pixels, a spatiotemporal modulation concept is introduced for spectrum detection.

The underlying mechanisms by which boron mitigates copper toxicity in Citrus sinensis leaves revealed by integrated analysis of transcriptome, metabolome and physiology.

Both copper (Cu) excess and boron (B) deficiency are often observed in some citrus orchard soils. The molecular mechanisms by which B alleviates excessive Cu in citrus are poorly understood. Seedlings of sweet orange (Citrus sinensis (L.) Osbeck cv. Xuegan) were treated with 0.5 (Cu0.5) or 350 (Cu350 or Cu excess) μM CuCl2 and 2.5 (B2.5) or 25 (B25) μM HBO3 for 24wk. Thereafter, this study examined the effects of Cu and B treatments on gene expression levels revealed by RNA-Seq, metabolite profiles revealed by a widely targeted metabolome, and related physiological parameters in leaves. Cu350 upregulated 564 genes and 170 metabolites, and downregulated 598 genes and 58 metabolites in leaves of 2.5μM B-treated seedlings (LB2.5), but it only upregulated 281 genes and 100 metabolites, and downregulated 136 genes and 40 metabolites in leaves of 25μM B-treated seedlings (LB25). Cu350 decreased the concentrations of sucrose and total soluble sugars and increased the concentrations of starch, glucose, fructose and total nonstructural carbohydrates in LB2.5, but it only increased the glucose concentration in LB25. Further analysis demonstrated that B addition reduced the oxidative damage and alterations in primary and secondary metabolisms caused by Cu350, and alleviated the impairment of Cu350 to photosynthesis and cell wall metabolism, thus improving leaf growth. LB2.5 exhibited some adaptive responses to Cu350 to meet the increasing need for the dissipation of excessive excitation energy (EEE) and the detoxification of reactive oxygen species (reactive aldehydes) and Cu. Cu350 increased photorespiration, xanthophyll cycle-dependent thermal dissipation, nonstructural carbohydrate accumulation, and secondary metabolite biosynthesis and abundances; and upregulated tryptophan metabolism and related metabolite abundances, some antioxidant-related gene expression, and some antioxidant abundances. Additionally, this study identified some metabolic pathways, metabolites and genes that might lead to Cu tolerance in leaves.

Thermal control system of Space Laser Communication Payload

Abstract To ensure the high-quality communication requirements of laser communication payload, the thermal control system is designed. Firstly, the structure and optical system of laser communication payload are introduced. Secondly, the task characteristic is analyzed. Then, the thermal design of laser communication payload is carried out with thermal conduction, thermal insulation, thermal dissipation and heating. Finally, a thermal balance test is performed. The test results show that the temperature of the optical system is 20.9 °C∼22.1 °C, the temperature of the detector is 15.5∼20.7 °C, the temperature of the pointing mechanism is 14.9 ∼ 17.5 °C, the temperature of the star sensor is 9.9 ∼ 18.7 °C, the temperature of the base is 13.9 ∼ 21.8 °C, and the temperature of the electric box is 14.7 ∼ 22.8 °C. The results of the test satisfy the requirements of the temperature indicators, indicating that the thermal design scheme is reasonable and feasible.

Water fluxes and energy partitioning over a Larix principis-rupprechtii plantation forest in a dryland mountain ecosystem, Northwest China

Plantations make up a sizable component of forest ecosystems in China's drylands and play an important role controlling the energy balance and water cycle. However, there is limited knowledge regarding the exchange of water and energy in dryland plantations, particularly those located within the intricate and unique environments of dryland mountain regions. The focus of this study was the investigation of a Larix principis−rupprechtii plantation within a dryland mountain ecosystem located in Northwest China. The eddy covariance method was employed to calculate the water and energy fluxes, while the thermal dissipation probe (TDP) method was utilized to measure forest overstory transpiration (T) from 2018 to 2021. The links between energy allocation and various components in water flux were investigated, as well as the variable dynamics of water and energy flux and their relationship with environmental conditions. The findings demonstrated that the annual mean cumulative evapotranspiration (ET) was about 510 mm, accounting for over 82.8 % of the precipitation, which was mainly from soil evaporation and understory transpiration, rather than overstory transpiration (T). The average value of T/ET was 0.25 for the growing season, and surface conductance (Gs) was always higher than canopy conductance (Gc) on both daily and monthly scales. The evaporative fraction (EF) and Priestley-Taylor model coefficient (α) in the growing season were significantly higher than those in the non-growing season, and α>1 from June to September, indicating that the ecosystem in the study area had sufficient water supply. Furthermore, during the growing season, the ratio of latent heat flux (LE) to net radiation (Rn) was larger than that in the non-growing season, while the proportion of sensible heat flux (H) was opposite, and soil heat flux (G) accounted for the smallest proportion of net radiation. This study provides valuable insights into the energy fluxes and water fluxes within the ecosystem of dryland mountain plantations, and it serves as a guide for choosing afforestation tree species in the future.

Design of temperature measurement system guided by thermal dissipation coefficient of NTC thermistor

NTC thermistors are widely used in temperature measurement instruments due to their excellent characteristics, including high accuracy, high sensitivity, and low cost. However, the self-heating generated during their operation affects the accuracy of temperature measurements. To solve this issue, the thermal dissipation coefficients of NTC thermistors are measured in various temperature environments. For the temperature range of −40°C to 120°C, the thermal dissipation coefficient varies from 2.35 mW/°C to 2.8 mW/°C. Considering the actual circuit design, the thermal dissipation coefficient measured at a temperature increase of 15 °C is used for subsequent calculations. The maximum operating power and current that do not affect the accuracy of temperature measurement are calculated based on the coefficient. Using this as a guide, the values of the voltage divider and reference voltage are determined. The actual operating current is only half of the maximum theoretical current. The temperature measurement system, based on NTC thermistors, is designed with the constant voltage source voltage divider circuit. The temperature measurement error of the system is less than 0.08 °C. It is confirmed that NTC thermistors perform well as temperature probes under suitable circuit design.

A self-satisfying cooling system based on cold energy storage for the locomotive in a high geothermal tunnel

Effective thermal management of locomotive systems is crucial for ensuring the safe operation of trains through high geothermal tunnels. By taking advantage of the frequent alternation of high-temperature tunnels and cold climate environment, a self-satisfying cooling system based on cold energy storage is proposed, in which a phase change heat exchanger between air and phase change material (succinic acid with 20 wt% expanded graphite) is developed to store cold energy outside tunnels and improve air-cooling efficiency inside tunnels. Numerical models are established to examine the thermal environment in a typical tunnel and the effectiveness of the proposed cooling system. The results indicate that because of the heat exhausted from the train and the thermal dissipation from the surrounding hot rock, the air temperature in the tunnel can rise above 50 °C. The proposed cooling system can release the cold energy from phase change material to keep the air outlet temperature below 40 °C, increasing the energy efficiency and reliability of locomotive operation. By examining the effects of locomotive operating conditions and orthogonal analysis of multi-factors, the heat exchanger structure and other operating conditions are recommended for the self-satisfying cooling system. Finally, the cooling system’s effectiveness is confirmed for the full-line operation of the locomotive along the Ya’an-Nyingchi section of the Sichuan-Tibet Railway in both summer and winter climatic conditions. This study is significant because it provides a novel design scheme for locomotive’s thermal management in high geothermal tunnels and other similar engineering conditions with natural cold sources.

Dynamic position optimization of submerged array square jet cooling in confined space for chip thermal dissipation

Jet position has a significant influence on the heat transfer characteristics of the chip. Therefore, it is necessary to optimize the jet position to improve its operating performance. Besides, traditional and typical optimization method is to establish abundant experimental/numerical models, which is very complicated and time-consuming, and the accuracy and effectiveness of results still need to be verified. Hence, a dynamic optimization method is proposed in this study and the jet position is directly controlled during the simulation process based on dynamic regulation of user-defined functions, which is directly related to the real-time physical quantities and the user-defined optimization strategy. Results show that compared to traditional jet position, the maximum temperature and temperature dispersion for the optimal jet position decrease by an average of 25.20 °C and 69.88 %, respectively. Furthermore, the optimal jet position efficiently achieves the balance between thermal performance and power consumption. To sum up, compared with manual optimization method, the dynamic optimization method proposed in this study only needs to establish one model and simulate it once to obtain the optimized result. This process is very convenient, high-efficiency and less time-consuming, which will be especially beneficial to effectively enhance the performance of the chip thermal dissipation.

Generation of cubic Hermite spline-based trochoidal milling toolpath by introducing a coefficient factor in machining curved slots

Trochoidal milling has become popular in high-speed milling due to its ability to reduce cutting force, enhance thermal dissipation, and prolong tool life. Among other toolpath patterns, the cubic Hermite spline offers significant advantages in generating trochoidal milling toolpath in machining complex and curved slots. However, determining those two different relation coefficients in the polynomial function of cubic Hermite spline remains complicated and empirical. This paper introduces a coefficient factor to simplify the determination process, which only requires the position and tangent vector parameters of each endpoint pair. The coefficient factor combines an instantaneous in-process slot width (IISW)-related width factor and a tangent vector direction-related direction factor. Two complex-curved slots are used to validate the performance of the proposed method. The results show that this method is straightforward and effective in generating trochoidal milling toolpaths for machining complex-curved slots while matching the slot geometry. Additionally, compared with a direct 5-axis trochoidal milling (one-step slotting strategy) in trochoidal milling of 3D slots on both serial and hybrid machining tools, a two-step slotting strategy (3-axis trochoidal milling and a successive 5-axis perpetual milling) is preferable in improving machining efficiency.

Dielectric and thermal conductive properties of differently structured Ti3C2Tx MXene-integrated nanofibrillated cellulose films

The fabrication of nanocellulose-based substrates with high dielectric permittivity and anisotropic thermal conductivity to replace synthetic thermoplastics in flexible organic electronics remains a big challenge. Herein, films were prepared from native (CNF) and carboxylated (TCNF) cellulose nanofibrils, with and without the addition of thermally conductive multi-layered Ti3C2Tx MXene, to examine the impact of polar (− OH, − COOH) surface groups on the film morphological, moisturizing, dielectric, and thermal dissipation properties. The electrostatic repulsion and hydrogen bonding interaction between the hydrophilic surface/terminal groups on CNF/TCNF and MXene was shown to render their self-assembly distribution and organization into morphologically differently structured films, and, consequently, different properties. The pristine CNF film achieved high intrinsic dielectric permittivity (ε' ~ 9), which was further increased to almost ε' ~ 14 by increasing (50 wt%) the MXene content. The well-packed and aligned structure of thinner TCNF films enables the tuning of both the composite’s dielectric permittivity (ε' ~ 6) and through-plane thermal conductivity (K ~ 2.9 W/mK), which increased strongly (ε' ~ 17) at higher MXene loading giving in-plane thermal conductivity of ~ 6.3 W/mK. The air-absorbed moisture ability of the films contributes to heat dissipation by releasing it. The dielectric losses remained below 0.1 in all the composite films, showing their potential for application in electronics.Graphic abstract

Honeycomb porous regenerated cellulose aerogel films with enhanced thermal dissipation for agricultural mulch application

Agricultural films, essential to contemporary agricultural production, are mostly made from non-biodegradable petroleum-based materials. The use of such films, especially in high-temperature environments, contributes to elevated internal temperatures in direct sunlight, adversely affecting crop appearance and quality. In this work, rice straw was used as the raw material to prepare biodegradable chemically crosslinked regenerated cellulose aerogel films (RCAF-CC) by combining physical dissolution regeneration, chemical cross-linking, and freeze-drying. The resulting RCAF-CC is notable for its high middle-infrared emissivity and high solar reflectivity, which significantly aid in thermal dissipation for agricultural mulch by enhancing infrared radiation and solar reflection. Compared to traditional polyethylene films, RCAF-CC, with its superior radiative cooling properties and lower water vapor transport rate, has a significant advantage in the growth trend and survival rate of cherry radishes. It is worth noting that the RCAF-CC achieved the degradation rate of 74.4 % in the 100-day soil burial experiment, and the soybean seeds grown in the degraded soil grew well, showing excellent eco-friendliness. These results show that RCAF-CC can be an alternative source of traditional agricultural films, solving the problems of non-biodegradable and high internal temperatures of the films under direct sunlight.

Oscillatory onset of rotating thermal convection subject to spatially varying magnetic fields and stable stratification

Convective fluid motions in deep planetary cores induce spatially and temporally varying magnetic fields observable as secular variation. Oscillatory instabilities occurring as onset modes in rapidly rotating thermal convection influenced by heterogeneous magnetic fields and stratification, investigated in this study, can be potentially linked to such observations. A plane layer approximation to near-polar and near-equatorial regions of the Earth's outer core is considered. In addition to penetrative convection and flow suppression effects, the simultaneous interaction of convective instabilities with asymmetrical magnetic fields and stable stratification is the focus of this study. The fundamental modes of magnetoconvection onset are preserved even under stable stratification, although the convection threshold is lowered irrespective of the parameter regime. The axial invariance of rapidly rotating columnar convection loses its midplane symmetry with intense localization of kinetic energy in the unstably stratified regions. The parameter regimes supporting the onset of the magnetically modified viscous oscillatory (mVO) modes are further extended toward Earthlike conditions such as high thermal conductivity (low Prandlt number, Pr) and magnetic dissipation (low Roberts number, q). Moreover, compared to fully unstable stratification, partial stable stratification enhances the range of imposed magnetic field length scale (δ) over which the onset of mVO modes is favored. The critical field length scale (δ⋆), above which the onset regime of the mVO modes is bounded by a minimum q, is determined. Irrespective of the rotation rate, below δ=δ⋆, the onset of the mVO mode is supported for asymptotically small q for Pr values close to the Earth's outer core.

Impingement of vortex dipole on heated boundaries and related thermal plume dynamics

The profound influence of an externally induced vortex dipole on thermal plume dynamics is numerically studied for varying Rayleigh numbers (Ra) employing the Bhatnagar–Gross–Krook collision model-based lattice Boltzmann method with a double distribution function approach. This study is extended to vortex dipole impingement with different types of heated bottom boundaries of two-dimensional domain, such as flat, “V-shaped,” and “inverted-V-shaped.” The vortex dipole impingement with the heated boundaries generates secondary vortices, which in turn produce vortex-driven thermal plumes, thereby advancing plume generation. The subsequent merging of the plumes enhances heat transport and leads to a continuous plume ascent. The presence of convex corners facilitates flow separation and also gives rise to the formation of secondary vortex dipoles, thereby significantly impacting the continuous generation of jet-like plumes when compared to concave configurations. The lack of an external vortex in pure buoyancy-driven flows produces less pronounced jet-like plumes and a relatively low Nusselt number. The boundary types and Ra significantly influence the vorticity production, resulting in higher enstrophy and palinstrophy for convex boundaries compared to flat and concave ones. A lower Prandtl number increases secondary vortices and corner rolls, leading to larger velocity gradients, higher thermal diffusivity, resulting in increased kinetic energy and thermal dissipation rates. The increased cell height enhances heat transfer at the top boundary due to improved heat convection from the slanted boundary and influence of early dipole impingement. Furthermore, kinetic energy dissipates in the dipole-driven flows and increases in the buoyancy-dominated flows.

Dynamic Power Saving for CMOS Circuits

With more functionalities being integrated into a microchip today, higher processing power is drawn. As a result of this, clock and logic power consumption has turned out to be a critical issue to be coped with by chip designers. In this paper, we present various power-saving approaches employed in complementary metal oxide semiconductor (CMOS) circuit designs. The approaches involve restructuring the logic circuits, performing clock gating, and selecting the appropriate circuits for counters and frequency divisions. In order to show their efficacies in power optimization, the approaches were applied to a phase-locked loop (PLL), clock divider (CD), full adder (FA), counter, arithmetic logic unit (ALU), and microprocessor without interlocked pipelined stages (MIPS) circuits and validated using Intel Quartus Prime Lite and Mentor Graphics Modelsim. The following conclusions can be drawn from the results: Firstly, the efficacy of minimizing power dissipation using logic restructuring is found to be in direct proportion with the rate of the switching activity (SA); secondly, a maximum of 3.5% of thermal power dissipation can be saved using clock gating; thirdly, gray counters give the lowest power consumption; and, finally, the thermal power estimation for the phase-locked loop (PLL) is relatively higher than that for the clock divider (CD) when both of them are implemented for dividing frequencies.

STUDYING HOW DIESEL ENGINE ADDITIVES USING SILVER OXIDE (Ag2O) NANOPARTICLES AFFECT THE ENVIRONMENT

Abstract: Biodiesel has been defined as an alternative fuel that has the potential to be used instead of diesel fuel for years. In case of complete combustion reaction in engines, the products released do not directly threaten human health. Compared to diesel fuel, biodiesel has worse combustion performance due to some fuel properties. Therefore, incomplete combustion products such as hydrocarbon (HC), carbon monoxide (CO), nitrogen oxide (NOx), smoke emission and complete combustion products such as CO2 are thrown into the atmosphere. In this study, the changes in exhaust emissions of 50 ppm and 75 ppm Ag2O NPs were experimentally examined to improve the adverse combustion performance and emission characteristics of cottonseed oil methyl ester. In experiments, nano additive improved the thermal conductivity, mass dissipation and heat transfer of the test fuels, and resulted in reducing of CO emissions as it provided a higher oxidation rate of hydrocarbon molecules. Due to the improvement in the combustion reaction, CO2 emission increased with product of complete combustion. The increase in CO2 emissions was 3.17% and 3.97% for CAg-50 and CAg-75 fuels, respectively, when compared to C0 fuel at 40 Nm load. The NPs additive increased the lower calorific value of the fuel and cylinder temperature. This situation caused increase of NOx emissions by 3.69% and 7.47% CAg-50 and CAg-75 fuels 40 Nm load. Adding of NPs in base fuel reduced to viscosity and density provided better atomization. So a reduction in smoke emission was obtained with NPs addition by 35.09% and 47.32% in CAg-50 and CAg-75 fuels, respectively, compared to C0 fuel at 10 Nm load, while 7.45% and 19.43% at 40 Nm load.