Coolant Inlet Temperature Research Articles

Novel multistage flash reversal Concept: Modelling and analysis

In this study, a rigorous modeling and simulation of a novel multi-stage flash (MSF) configuration consisting of reversing the brine circulation, termed MSF reversal (MSF-RV), is developed. Its performance is theoretically investigated and compared with conventional MSF Once Through (MSF-OT) with and without brine mixing. The MSF-RV concept is suitable for treating geothermal streams and can be driven by low grade thermal energy such as solar and geothermal energy and waste heat for direct seawater desalination. Hence, two options of MSF-RV are proposed, i) driven by a direct hot stream (MSF-RVc), and ii) powered by external heat to treat raw seawater (MSF-RVh). The analysis showed that the temperature distribution throughout the stages plays a significant role in the thermal efficiency and heat transfer area requirements for both configurations. Hence, careful selection of the design parameters is necessary to achieve the best performance. For the same recovery ratio, the MSF-RVc was found superior to MSF-OT in terms of gain output ratio (GOR) and specific energy consumption (SEC) by 52% and 60%, respectively. However, the specific area (sA) requirement of MSF-RVc is higher than that of MSF-OT by 50%. Brine mixing by recycling the rejected brine enhances the recovery ratio, GOR, and SEC for both structures. Conversely, the sA requirement increases with brine mixing but marginally for MSF-RV and remarkably for MSF-OT. Moreover, the design parameters of MSF-RVc such as the coolant inlet temperature, the temperature drop on the coolant side, and the coolant to brine ratio affect the overall performance. However, a trade-off between the thermal efficiency (GOR, SEC) and surface area requirement is still observed.

Uncertainty analysis of operational conditions in selective artificial ground freezing applications

Artificial ground freezing (AGF) systems are susceptible to uncertain parameters highly affecting their performance. Particularly, selective artificial ground freezing (S-AGF) systems involve several uncertain operational conditions. In this study, uncertainty analysis is conducted to investigate four operational parameters: 1) coolant inlet temperature, 2) coolant flow rate, 3) pipes emissivity, and 4) pipes eccentricity. A reduced-order model developed and validated in our previous work for field-scale applications is exploited to simulate a total of 5,000 cases. The uncertain operational parameters are set according to Monte Carlo analysis based on field observations of a field-scale freeze-pipe in the mining industry extending to 460 m below the ground surface. The results indicate that the freezing time can range between 270 and 350 days with an average of 310 days, whereas the cooling load per one freeze-pipe ranges from 90 to 160 MWh, with an average of 129 MWh. Furthermore, it is observed that the freezing time and energy consumed are mostly dominated by the coolant inlet temperature, while energy dissipated in the passive zone (where ground freezing is not needed) is mostly affected by pipes emissivity. Overall, the conclusions of this study provide useful estimations for engineers and practitioners in the AGF industry.

Investigation on heat transfer during transpiration cooling with hydrocarbon fuel coolant

The article presents a numerical approach to investigate the transpiration cooling problems with coolant cracking reaction inside porous media. The effects of cracking reaction, coolant mass flow rate per unit area, coolant inlet temperature and heat flux distribution on porous wall on the transpiration cooling are studied. Studies have shown that the cracking reaction of hydrocarbon fuels can greatly improve the heat absorption caused by only physical heat sink, and the heat sink ratio can exceed 1 near the outlet of the porous media. The cracking reaction can improve the solid temperature uniformity of porous media at the inlet, but has a negative impact on that at the outlet, and the temperature difference between the fluid and the solid increases at the outlet of the porous media because the small molecular products produced by the cracking have a smaller specific heat capacity. The occurrence of the cracking reaction reduces the flow Reynolds number of the fluid inside the porous media, and the convective heat transfer coefficient is limited. Small-molecule products from cracking enhance thermal dispersion inside porous media, which is conducive to the transfer of local high heat to the surrounding area and reduces thermal stress.

Possible power increase in a natural circulation Soluble-Boron-Free Small Modular Reactor using the Truly Optimized PWR lattice

In this study, impacts of an enhanced-moderation Fuel Assembly (FA) named Truly Optimized PWR (TOP) lattice, which is modified based on the standard 17 × 17 PWR FA, are investigated in a natural circulation Soluble-Boron-Free (SBF) Small Modular Reactor (SMR). Two different TOP lattice designs are considered for the analysis; one is with 1.26 cm pin pitch and 0.38 cm fuel pellet radius, and the other is with 1.40 cm pin pitch and 0.41 cm fuel pellet radius. The NuScale core design is utilized as the base model and assumed to be successfully converted to an SBF core. The analysis is performed following the primary coolant circulation loop, and the reactor is modelled as a single channel for thermal-hydraulic analyses. It is assumed that the ratio of the core pressure drop to the total system pressure drop is around 0.3. The results showed that the reactor power could be increased by 2.5% and 9.8% utilizing 1.26/0.38 cm and 1.40/0.41 cm TOP designs, respectively, under the identical coolant inlet and outlet temperatures as the constraints.

Study of Two-Phase Microchannel Heat Sink Fabricated by A.M. Technology for Energy Reuse in the Electronic Device

Data centers’ electricity energy consumption accounts for 1% of global electricity demand and 0.3% of all global CO2 emissions. Energy reuse as a core of a net zero carbon data center, as a macro goal benefiting to mankind, needs micro innovations from thermal engineers to reclaim the distributed and low-grade thermal energy from diversified electronic equipment. This article presents the attempt to combine the advantages of high-density heat transferring technology by two-phase microchannels and the agility of Additive Manufacturing (A.M.) technology into a heat sink by which thermal energy can be collected in premium quantity and quality. The heat sink prototype adopted the two-layer microchannel design by leveraging the unique capability of A.M. technology to form complicated spatial geometric features, such as the functional channel profiles with diverged cross-sections along the flow direction, intermittent channels, and curved channels. It was fabricated at one-time processing by AlSi10Mg powder SLS/SLM, had an exterior base area of 25 cm2, and interior micro-fins with a minimal thickness of 0.2 mm and fin pitch of 0.38 mm. A test rig had been built to validate the thermal dynamic and hydraulic performance of this microchannel heat exchanger working with HFE 7100 as the coolant. The heat flux under certain wall superheat and pressure drop catches the equivalent grade of microchannels made by conventional micro-cutting approaches on copper or aluminum. The maximum inlet coolant temperature could be elevated up to 60.0 °C with less than 90.0 °C CPU case temperature, which provides the feasibility of high-grade heat recovery. The test results present the promising prospects of this design and A.M. technology in the field of two-phase microchannel heat exchanging, by which the electronic devices in megawatt hyperscale data center can be changed from energy consumers to energy generators for the greenhouse, district heating, and hot water system.

CFD simulation of partial channel blockage on plate-type fuel of TRIGA-2000 conversion reactor core

A nuclear reactor cooling system that has been operating for a long time can carry some debris into a fuel coolant channel, which can result in a blockage. An in-depth two-dimensional simulation of partial channel blockage can be carried out using FLUENT Code. In this study, a channel blockage simulation is employed to perform a safety analysis for the TRIGA-2000 reactor, which is converted using plate-type fuel. Heat generation on the fuel plate takes place along its axial axis. The modelling of the fuel-plate is in the form of a rectangular sub-channel with an inlet coolant temperature of 308 K with a low coolant velocity of 0.69 m/s. It is assumed that blockage is in a form of a thin plate, with the blockage area being assumed to be 60 %, 70 %, and 80 % at the sub-channel inlet flow. An unblocking condition is also compared with a steady-state calculation that has been done by COOLOD-N2 Code. The results show that a partial blockage has a significant impact on the coolant velocity. When the blockage of 80 % occurs, a maximum coolant temperature locally reaches 413 K. While the saturation temperature is 386 K. From the point of view of the safety aspect, the blockage simulation result for the TRIGA-2000 thermal-hydraulic core design using plate-type fuel shows that a nucleate boiling occurs, which from the safety aspect, could cause damage to the fuel plate.

A Model Predictive Controller for the Core Power Control System of a Lead-Cooled Fast Reactor

To study the model predictive control (MPC) for a lead-cooled fast reactor's core power control system (LFR), firstly, the LFR core is established with the state space model. Then, to establish an LFR core power control system, a predictive model controller is used. Finally, the conditions of 20pcm step reactivity and 5% step down of coolant inlet temperature are introduced to study the control characteristic. The maximum overshot (MO) and the transient time are calculated in the time domain, and the stability of the core power control system is analyzed using the Nyquist and Bode diagrams in frequency domains. The result shows that the MPC controller and PID controller are feasible in core power control, and the core power control systems are closed-loop stable systems.

Research on core power maximization method of natural circulation lead-bismuth cooled fast reactor

To improve the inherent safety and cost-effectiveness of lead-bismuth cooled fast reactors, the SPALLER-100 reactor designed by the University of South China has been selected as the research object to determine the maximum power it can produce. This is a multi-objective, complex, multi-dimensional, nonlinear, and constrained optimization problem. To maintain the transportability, material durability, and long-term operation stability of the reactor core and ensure safety under accident conditions, three steady-state limitations and three accident limitations are proposed. The platform used to calculate the maximum neutronic power produced by the reactor at different core heights has been built using Latin hypercube sampling and the Kriging proxy model. Meanwhile, the cooling power of the reactor at different core heights is calculated by considering its natural circulation capacity. Finally, a design scheme is obtained that meets the requirements of neutronic and thermal-hydraulic assessments, while producing maximum power. Consequently, during the entire life-cycle of SPALLER-100, a safety analysis of three typical accident scenarios (unprotected loss of heat sink, unprotected transient over power, and unprotected coolant inlet temperature undercooling) is performed using a Quasi-Static Reactivity Balance (QSRB) approach. The results show that the platform used to calculate the maximum neutronic power exhibits high accuracy, and that the design scheme with maximum power is safe and economical. Overall, this study can provide reference ideas for designing natural circulation reactors that can maximize power output.

Low-cost numerical lumped modelling of lithium-ion battery pack with phase change material and liquid cooling thermal management system

This study is aimed at developing a low cost lumped model for simulating a Li-ion battery pack with thermal management systems (TMS) under continuous charging/discharging cycles. The considered system is composed of twenty-four commercial Li-ion batteries with phase change material (PCM) and nine aluminium tubes for liquid coolant circulation. A zero-dimensional numerical model is developed based on the transient energy balances and the analogy between heat transfer and electrical transfer using resistances and capacitors. The simulations were carried at 3-C discharging/0.5-C charging rates and obtained results were compared with both three-dimensional computational fluid dynamic (CFD) results and experimental results from the literature. The effect of various system design and operating characteristics such as the cooling method, the coolant temperature and its velocity, the number of coolant pipes and the ambient conditions on the system performance were presented and analysed. Results show that combining both PCM and liquid cooling for battery thermal management leads to reduce the maximal battery temperature by about 38 °C and 4 °C compared to natural convection thermal management mode and to passive PCM thermal management mode, respectively. Increasing the number of cooling pipes improves the performance of the system and its optimal number in this system is up to 9 pipes. The maximal battery cells temperature is reduced from 31 °C to 20 °C as the used liquid coolant inlet temperature is reduced from 25 °C to 10 °C. Finally, the suggested low cost lumped model is a promising tool for simulating, designing and optimising battery pack with thermal management systems under real exploitation conditions.

Determination of heat flux leading to the onset of flow instability in MTR reactors

Abstract The prediction of heat flux leading to the Onset of Flow Instability (OFI) phenomena is an important consideration in the design of Material Testing Reactors (MTR) due to the possibility of flow excursion during postulated accident. From the thermal-hydraulic point of view, OFI is the critical phenomenon limiting MTR reactor power. In a previous work, an empirical correlation is developed to predict the subcooling at OFI in narrow vertical rectangular channels simulating a coolant channel of MTR. In the present work, an innovative model to determine the heat flux leading to OFI in MTR reactors is introduced based on the previous correlation. The developed model gives a very low deviation of only 1.65% from the experimental data of Whittle & Forgan that covers a wide range of MTR operating conditions. The heat flux leading to OFI is also predicted by both Whittle & Forgan and Fabrega correlations for comparison. The present model is then applied on the IAEA 10 MW MTR generic reactor to predict the Best-Estimate (BE) and Best-Estimate-Plus-Uncertainty (BEPU) Onset of Flow Instability Ratio (OFIR) and the power leading to OFI as well as the bubble detachment parameter under different coolant velocities and inlet temperatures. The model is also used to predict both the OFIR and bubble detachment parameter in the reactor under unprotected Loss-of-Flow transient for exponential flow decay with a time constant of 1.0 s (fast LOFA), 10, 15 and 25 s (slow LOFA) from a power level of 10 MW. For BEPU calculation, a combined statistical method with direct propagation of errors is adapted to treat the uncertainty factors for fuel fabrication and measured parameters in the BEPU calculation. The model results is analyzed and discussed.

Design and Thermal Analysis of a 3-D Printed Impingement Pin Fin Cold Plate for Heterogeneous Integration Application

Miniaturization high heat flux of power electronic devices have posed a colossal challenge for adequate thermal management. Conventional air-cooling solutions are inadequate for high-performance electronics. Liquid cooling is an alternative solution due to the higher specific heat and latent heat associated with the coolants. Liquid-cooled cold plates are typically manufactured by different approaches, such as skived, forged, extrusion, and electrical discharge machining. When researchers are facing challenges in creating complex geometries in small spaces, 3-D-printing can be a solution. In this article, a 3-D-printed cold plate was designed and characterized with water coolant. The printed metal fin structures were strong enough to undergo pressure from the fluid flow even at high flow rates and small fin structures. A copper block with the top surface area of 1 in <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\times \,\,1$ </tex-math></inline-formula> in was used to mimic a computer chip. Experimental data have good match with a simulation model, which was built using commercial software 6SigmaET. Effects of geometry parameters and operating parameters were investigated. The fin diameter was varied from 0.3 to 0.5 mm and the fin height was maintained at 2 mm. A special manifold was designed to maximize the surface contact area between coolant and metal surface and therefore minimize thermal resistance. The flow rate was varied from 0.75 to 2 L/min and the coolant inlet temperature was varied from 25 °C to 48 °C. It was observed that for the coolant inlet temperature 25 °C and aluminum cold plate, the junction temperature was kept below 63.2 °C at an input power of 350 W and the pressure drop did not exceed 23 Kpa. Effects of metal materials used in 3-D-printing on the thermal performance of the cold plate were also studied in detail.

A SiC-Based Liquid-Cooled Electric Vehicle Traction Inverter Operating at High Ambient Temperature

This paper describes the design process of a high-power-density 100 kW (34 kW/L) traction inverter for electric vehicles, operating at an ambient temperature of 105 °C. A detailed thermal analysis is performed based on the thermal behavior of the switching devices, and the results are used to estimate the semiconductor device junction temperature and to determine the requirements of the cooling system to achieve the target power level. A high-temperature gate drive board aiming for reliable system operation in electric vehicles is developed. An overcurrent protection scheme based on parasitic inductance between the power source and the Kelvin source of the power module has been implemented. A dc-link decoupling snubber circuit is designed numerically based on a detailed forth-order high-frequency equivalent circuit of a double pulse test circuit. The approach to optimize the snubber circuit, not only for the voltage spike suppression but also for good thermal performance, is proposed. Finally, a hardware prototype with SiC power modules has been built and tested at 60 kW continuous power and 100 kW for 20 seconds at 105 °C ambient temperature and 65 °C inlet coolant temperature.

Модель реактивнісної аварії на РБМК-1000

The reactor model was used to study the accident that destroyed the RBMK-1000 reactor at Unit 4 of the Chornobyl nuclear power plant on 26 April 1996. The model of reactivity accident of the RBMK-1000 reactor is based on equations of nuclear reactor kinetics, taking into account feedback in reactor reactivity. Reactivity changes as a result of both external influences – the movement of regulatory organs, changes in the reactor inlet coolant temperature, – and as a result of feedback by core parameters – changes in fuel temperature, coolant density, and 135Хе concentration. The model takes into account steam generation in the reactor core, which corresponds to the real physics of processes at the RBMK reactor, and allows obtaining simulation results that best match the recorded data and the consequences of the accident process. The study of reactivity accident on RBMK-1000 reactor is carried out for different combinations of values of control rods efficiency; reactivity coefficients by fuel temperature and coolant density; changes in the reactor inlet coolant temperature; the emergency protection time, as well as the reactor power level before closing the turbine generator stop valve. Different reactivity accident scenarios at RBMK-1000 reactor allow us to determine the most unfavorable combinations of external influences on the course of reactivity accident, namely: start time of main coolant pump rundown, time of activation of emergency protection, power level before the closing of turbine generator stop valves. In most reactivity accident scenarios, first of all, the critical values of fuel enthalpy are reached, at which the process of fuel destruction in the fuel element, destruction of the fuel assembly, and assembly channel start. Important results of studies are 1 – determination of the fact that time of activation of emergency protection after the closing of stop valves of turbine generator significantly affects the value of the maximum neutron power that is achieved during a reactivity accident; 2 – determination of the effect of reactor power before the closing of turbine generator stop valves on the course of the accident; 3 – it is not necessary to achieve supercritical on instantaneous neutrons, supercritical on delayed neutrons is enough to start fuel destruction.

Numerical Investigation of Heat Transfer Performance of Microchannel with Wall-Mounted Obstacles Using Hybrid Nanofluids

In the present study, the thermal performance of a microchannel with rectangular, triangular and circular shaped wall-mounted blocks on the top and bottom walls are studied numerically using hybrid nanofluids (Cu+Al/water, Cu+Al2O3/water, Ag+CuO/water, Ag+Al2O3/water) and ionic Nanofluid (Al2O3/[C4mim] [NTf2]). A constant Reynolds number equal to 10, volume fraction for first and second nanoparticle as 0.1 and 0.05 respectively, wall temperature of 27°C and coolant inlet temperature of 20°C are considered. The microchannel with triangular block showed maximum heat transfer performance. The Nusselt number of the microchannel with triangular blocks and nozzle at the inlet was enhanced by 145.76%. The maximum Nusselt number has been found for (Ag+Al2O3)/water hybrid nanofluid which is 13.8 %, 30 %, 37.12 % and 640 % greater as compared to (Ag+CuO)/water, (Cu+ Al2O3)/water, (Cu+ Al)/water and base fluid respectively. The microchannel with ionic nanofluid enhanced by 208 % as compared to water.

Comparison of Commonly Used Cooling Concepts for Electrical Machines in Automotive Applications

The thermal design of electrical machines has numerous influencing factors. This paper compares different cooling methods, their volume flow rates and other machine parameters with regard to the continuous power of a PMSM. Understanding the characteristics of different heat sinks depending on their operating point is important for an expedient design in order to avoid derating due to overtemperatures. As a design guideline, this contribution shows the influence of stator cooling jackets, rotor shaft cooling and direct end winding cooling for different machine lengths and volume flow rates. Both water and oil are investigated as coolants. With increasing machine dimensions, end winding cooling becomes less effective for heat sources in the center of the machine while the heat transferred in the cooling jacket increases. A sensitivity study of other machine parameters, such as the maximum allowed magnet temperature or the coolant inlet temperature, improves the understanding of the reader as to how the continuous power of a PMSM can be increased when the rotor temperature limits the performance.

Performance Study on the Effect of Coolant Inlet Conditions for a 20 Ah LiFePO4 Prismatic Battery with Commercial Mini Channel Cold Plates

Rechargeable Li-ion batteries are widely used in renewable energy storage and automotive powertrain systems, and therefore, an efficient thermal management system is imperative for maximum battery life and safety. Battery heat generation and dissipation rates primarily depend on the battery surface temperatures, which are affected by the coolant system design and coolant inlet conditions. In this paper, a two-way coupled electrochemical-thermal simulation with selected experimental validation has been performed and analyzed the effect of water coolant inlet conditions on the effectiveness of commercial mini-channel cold-plates for 20 Ah LiFePO4 prismatic batteries. Three coolant inlet temperatures (25–45 °C) and four flow rates (150–600 mL/min) are tested at three different discharge rates (2–4 C) and the performance of coolant system design has been analyzed in terms of battery peak (maximum) temperature and temperature difference (i.e., non-uniformity) across the battery. The predicted results indicate that the coolant flow rate has a profound effect on the battery temperature non-uniformity, while the coolant inlet temperature has a significant effect on the battery peak temperature. At high coolant flow rates, the battery surface temperature difference is within the acceptable range (ΔT &lt; 5 °C), but the maximum temperatures are high at all discharge rates. Further, at the low coolant inlet temperature of 25 °C and the high coolant flow rate of 600 mL/min, the battery temperature rise at the top and bottom locations during the constant current discharge process is high, indicating that the battery heat generation rate is high at a low coolant inlet temperature.

Pre-conceptual high temperature gas cooled microreactor design utilizing two-phase composite moderators. Part II: Design space and safety characteristics

This work expands on a pre-conceptual microreactor design based on a High Temperature Gas-Cooled Reactor (HTGR) platform generated in the companion paper of this study. Here, power, coolant inlet temperature, and coolant outlet temperature are varied to outline an operable design space associated maximum allowable component temperatures and coolant pressure drop for a given microreactor design. Calculations show that beryllium- and hydride-based composite moderators have a smaller operating design space than graphite because of a lower allowable moderator temperature under the conservative upper limits employed for this study. Power below 6MWth was considered to be undesirable for all designs because of a limited inlet/outlet temperature range. Reactivity Temperature Coefficients (RTC) are calculated to illustrate an inherent safety feature of HTGRs and are fed into a Depressurized Loss of Forced Coolant (DLOFC) without active intervention accident simulation, considered to be a bounding case for fuel temperatures in a HTGR. RTC calculations showed that all designs would expect to have a negative isothermal coefficient through their entire operating cycle and DLOFC calculations showed no case exceed their maximum temperature limits. An additional accident that simulates the release of fission products is performed to compare expected minimum Emergency Planning Zone (EPZ) size for all designs. EPZ calculations showed a marginally smaller achievable size for the composite moderators because of a lower concentration of relevant nuclides due to a more thermal spectrum

A multilayered approach to scale-up forced convection-based freezing of human induced pluripotent stem cells

This work presents a multilayered model-based approach to scale-up slow and forced convection-based freezing of human induced pluripotent stem cells. The approach combines a hybrid single-cell freezing model (covering the cell and cryovial layers) with a computational fluid dynamics model (covering the freezer layer). The proposed approach can calculate the cell survival rate considering spatial and time-dependent temperature profiles within a freezer unit. The approach was first demonstrated on a single cryovial problem where it was found that the inlet coolant velocity affected the cell survival rate when fast cooling rates were applied. The freezing of 235 cryovials was then studied, where 18 operation conditions consisting of six cooling rates (three constant and non-constant cooling rates, respectively) and three inlet coolant velocities were investigated. The multilayered approach captured the spatial heterogeneity in the cell survival rates for a given inlet coolant velocity and temperature profile.

Heat transfer performance of an automotive radiator with MWCNT nanofluid cooling in a high operating temperature range

• An update review on nanofluids in an automotive radiator is presented. • Evaluation of the nanofluid stability using the UV–vis spectrophotometric method. • Thermophysical properties of MWCNT water/EG nanofluids are experimentally investigated. • Thermal performance of MWCNT nanofluids in a temperature range of 80–105 °C. • Observed agglomeration and sedimentation after experimental test in high temperature. This study investigates the heat transfer performance of multiwalled carbon nanotube nanoparticles (MWCNT) dispersed in a binary mixture of water-EG (ethylene glycol) at a volumetric ratio of 50:50 in an automotive radiator. The nanofluids were prepared using the two-step synthesis method at volumetric ratios of 0.025%, 0.05% and 0.1%. The UV–vis spectrophotometry method was used to evaluate the colloidal stability of the samples, reporting the absorbance-concentration relationship according to the Beer-Lambert law. Thermophysical properties such as thermal conductivity and viscosity were measured experimentally and compared with correlations in the literature. The influence of nanoparticle concentration as well as the coolant inlet temperature, of up to 105 °C, on the heat transfer rate and in the overall heat transfer coefficient were evaluated experimentally. The air velocity was maintained constant at 2 m/s and the coolant mass flow rate ranged between 0.09 kg/s and 0.11 kg/s. The maximum increases for the heat transfer rate and for the overall heat transfer coefficient were 4.6% and 4.4%, respectively. The results show that the increase in the concentration of nanoparticles can improve the performance in heat transfer, although the performance decrease for high nanofluid inlet temperatures in the radiator was significant. Finally, the stability of the nanofluids was reassessed after performing tests on the radiator, demonstrating high aggregation and sedimentation of nanoparticles.

Experimental Investigation of Heat Transfer Characteristics of Automobile Radiator using Tio2 Nanofluid Coolant

Abstract: The use of nanoparticle dispersed coolants in automobile radiators improves the heat transfer rate and facilitates overall reduction in size of the radiators. In this study, the heat transfer characteristics of water/propylene glycol based TiO2nanofluid was analyzed experimentally and compared with pure water and water/propylene glycol mixture. Two different concentrations of nano fluids were prepared by adding 0.1 vol. %, 0.2 vol. %, 0.3 vol. % and 0.4 vol. % of TiO2 nanoparticles into water/propylene glycol mixture (60:40). The experiments were conducted by varying the coolant flow rate between 3 to 6 lit./min. for various coolant temperatures (50°C, 60°C, 70°C, and 80°C) to understand the effect of coolant flow rate on heat transfer. The results showed that the Nusselt number of the Nano fluid coolant increases with increase in flow rate. At low inlet coolant temperature the water/propylene glycol mixture showed higher heat transfer rate when compared with Nano fluid coolant. However at higher operating temperature and higher coolant flow rate, 0.3 vol. % of TiO2nanofluid enhances the heat transfer rate by 8.5% when compared to base fluids. Keywords: Heat transfer enhancement, Propylene Glycol, Radiator, TiO2Nanofluid coolant