Improvement In Heat Transfer Rate Research Articles

Analysis on thermal and flow behavior of triple concentric tube heat exchanger handling MWCNT-water nanofluids

Design of heat exchangers and heat transfer enhancement methods are struggling to meet out the cooling demand of present scenario. Many researchers suggested that the addition of nanosized solids particles into traditional base fluids resulting the higher heat transfer rate than the existing coolants and named the new fluids as nanofluids. In this investigation, the effect of microwave carbon nanotube (MWCNT)-water nanofluids on heat transfer rate, pressure drop and pumping power of a triple concentric tube heat exchanger are experimentally investigated and compared the results of MWCNT-water nanofluids with water. The MWCNT-water nanofluids were prepared by two step method at the volume concentrations of 0.2%, 0.4%, and 0.6%. The range of target fluid mass-flow rate is in the range of 0.026 to 0.039 kg per second and the constant heat flux condition is considered. On experimentation, it is noted that the effectiveness and presure drop of 0.6% MWCNT-water based nanofluids are 27% and 21% greater than water at the maximum mass-flow rate. The reason for improved heat transfer rate of nanofluids is because of higher thermal conductivity, Brownian motion, lower boundary-layer thickness, and lower specific heat capacity of nanofluids. Also found that the pumping power increases with increasing volume concentration and pumping power is 25% higher than water at the 0.6% nanofluids. Therefore, the MWCNT-water nanofluids are good choice for replacing water as coolant in triple concentric tube heat exchanger.

Enhancement of thermal conductivity and thermal stability of capric-lauric acid eutectic phase change material using carbonaceous materials

This paper investigates the effect of adding carbon based nano additives viz., graphene oxide (GO), multi-walled carbon nanotubes (MWCNT) and activated carbon (AC) to capric-lauric acid (CA-LA) eutectic phase change material (PCM) in order to prepare nanoenhanced PCMs (NEPCMs). Field emission scanning electron microscopy images showed that GO has a sheet, MWCNT has a tube, and AC has a sheet with porous like structures, which influence the shape stability of eutectic PCM. The CA-LA has melting and solidification temperature at 18.92 °C and 18.30 °C, corresponding latent heat values were 107.9 J g−1 and 106.8 J g−1 analyzed by differential scanning calorimetry. The addition of carbonaceous materials shows a slight decrease in the latent heat values for NEPCMs which is quashed by its improved heat transfer rate. Thermal stability of NEPCMs were studied by thermogravimetric analysis. As-prepared carbonaceous materials had excellent thermo-physical properties in that MWCNT has higher thermal conductivity compared to GO and AC due to it light weight. Therefore, NEPCMs has acceptable thermal properties which are suitable for cold thermal energy storage.

Optimal Start-up Policies for a Nanofluid-Based Solar Thermal Power Plant

Parabolic trough solar thermal power plants use a fluid to transfer thermal energy from captured solar radiation to a Rankine cycle to drive a turbine that, coupled to an electrical generator, produces electricity. Continuous improvement on their performance will lead these technologies to truly compete with either conventional or other forms of renewable energy systems. Nanofluids have been proposed as a way to improve heat transfer rates in thermal solar plants. Hence, nanofluid thermal solar plants coupled to dynamic optimal operating policies should render improved heat transfer characteristics as well as power production. The main objective of this work is to obtain optimal start-up policies of such plants using diverse nanofluids (Al2O3-water and TiO2-water) compared against pure water as base fluid, focused on power delivery and the time required for the system to reach target conditions. For the analysis, the deterministic dynamic mathematical model of a previously proposed solar thermal power fac...

Laminar flow heat transfer enhancement in square and rectangular channels having: (1) A wire-coil, axial and spiral corrugation combined with helical screw-tape with and without oblique teeth and a (2) spiral corrugation combined with twisted tapes with oblique teeth

Heat transfer enhancement is a vital area of research as it helps to design heat exchangers of reduced sizes and improved heat transfer rates. Thus, there is a pressing need for techniques which result in significantly increased heat transfer over and above increased pressure drop. In this paper, the benefits of different compound techniques using (1) wire-coil inserts and helical screw-tape inserts with oblique teeth, (2) wire-coil inserts and helical screw-tape inserts without oblique teeth, (3) spiral corrugation and helical screw-tape inserts without oblique teeth, (4) axial corrugation and helical screw-tape inserts without oblique teeth, and (5) spiral corrugation and twisted-tape inserts with oblique teeth were studied experimentally for laminar flow in a non-circular duct (aspect ratio = 1, 0.5 and 0.33). Servotherm medium oil with Prandtl number ranging from 430 to 530 was used as working fluid. The experiment was conducted for a uniform heat flux boundary condition. The effect of geometric parameters of the inserts such as wire-coil diameter, wire-coil helix angle, tooth angle and tooth horizontal length of the screw tape and the twisted tape, corrugation height and corrugation pitch, etc. on heat transfer and pressure drop characteristics was presented. The influence of duct geometry (aspect ratio) on Nusselt number and friction factor was also studied. Correlations for Nusselt number and friction factor were developed and a performance evaluation was done.

A Study on Mixed Convection Flow in a Lid-Driven Cavity Filled With Micropolar Nanofluid by Considering Brownian Motion

The mixed convective heat transfer of a micropolar nanofluid in a square lid-driven cavity has been numerically studied. The lid is thermally insulated, the side walls are kept cold, and the bottom wall is kept hot with sinusoidally thermal boundary condition. The governing equations were solved by finite volume method using the SIMPLE algorithm. The effect of Grashof number (102–105), the volume fraction of nanoparticles (0.0–0.1), and micropolarity (0.0–2.0) has been investigated on the heat transfer of Al2O3–water nanofluid. Also, the variable model was used to calculate fluid viscosity and thermal conductivity coefficient of the nanofluid. The results showed that an increase in Grashof amplifies the buoyancy force and enhances the Nusselt number. Also, an increase in vortex viscosity at low Grashof numbers strengthens the forced convection and increases the Nusselt number over the bottom wall. However, at Gr = 105, the increase in vortex viscosity up to K = 1.0 leads to a decrease in the amount of heat transfer, but its further increase entails the increase in heat transfer. Although the addition of nanoparticles to the fluid improves heat transfer rate, the extent of improvement at nonzero K values is lower than that in the Newtonian fluid. The comparison of the average Nusselt number computed on the hot wall under two different states of temperature-depended thermo-physical properties and constant thermo-physical properties reveals that their difference is more significant for the Newtonian fluid especially at higher volume fraction.

Heat transfer enhancement and pressure drop by pulsating flow through helically coiled tube: An experimental study

Pulsating flow was applied as an active technique for heat transfer enhancement. Helically coiled tube was employed and convective heat transfer and pressure drop were experimentally investigated. Four helically coiled tubes with the same tube diameter and different coil curvature were fabricated and subjected to uniform wall heat flux. Distilled water was utilized as working fluid and its thermo-physical properties were estimated at mean temperature using available correlations. At first, Darcy friction factor and Nusselt number in steady laminar flow were compared with several correlations in the literature and the most accurate relations were found. Afterward, experiments were extended for pulsating laminar flow over a Womersly number range of 16–38 which corresponds to 2–10 Hz pulsating frequency, Reynolds number of 2000–9500, and Helical number of 350–2300. The results revealed that increment in pressure drop is nearly 3–7% in pulsating flow compared to steady one, while convective heat transfer enhanced up to 39%. Findings indicated that more heat transfer enhancement can be attained at low Reynolds numbers. Improvement in heat transfer rate and thermal performance was evaluated and discussed in detail. Also, a new correlation was proposed for Nusselt number in laminar pulsating flow. Among the four pulsating frequencies were studied in the current work, the optimum pulsating condition for achieving the best thermal performance was Wo ~ 24 (4 Hz).

Improving Efficiency of Cooling Coil Chiller Units

Air Cooled condensers were first introduced in US power industry in early 1970’s, but only during last 10-15 years number of installations greatly increased largely due to growing attention being paid to environmental safety. Also, growing demand for water for both domestic and industrial use has brought an increased interest in use of Air Cooled condensers. This is a review paper which studies the performance of Air-cooled condenser under various operating conditions it is found that there is degradation in performance of air cooled condenser under high ambient temperatures and windy conditions. The heat rejection rate of ACC also depends on surface condition of fins and thus its performance is reduced due to external fouling of finned tubes due to weather conditions and by internal fouling from condensate (Ammonia corrosion). A Hybrid (dry/wet) dephlegmator achieves major enhancement in performance when ambient temperatures are high. Also shading of condensers is done for air-conditioning units to mitigate the adverse effect of high ambient temperatures due to solar radiation. Now a day’s wind walls are used to reduce the effect of high wind velocity .second option is to increase the fan speed Fin cleaning plays an important role in heat rejection. External cleaning improves air side heat transfer coefficient. In order to improve the performance of an ACC Flat tubes inclined at some angle to horizontal can also be used in place of conventional circular horizontal tubes so that an improvement in heat transfer rate occurs.

Heat transfer and flow performance of a novel T type heat sink with GaInSn coolant

In order to improve heat transfer rate, a novel T type heat sink is proposed. The numerical and experimental researches are carried out on flow and heat transfer performance of the new heat sink. The new heat sink consists of six inlet ports and six outlet ports, which attribute to shorter flow channels. Higher Nusselt number and much better temperature uniformity of the heating surface are obtained due to short channels, the arrangement of the inlet and outlet in the new design compared to the traditional design. Then, the effects of four arrangements of inlets and channel number on the hydro-thermal performance are examined numerically. Both the Nusselt number and friction factor of the heat sink with eight inlets are the lowest, while the temperature uniformity is the best. The larger the channel number, the higher Nusselt number with lower pressure drop. This is because a reduction of the temperature rise for a part with more channels is found, although the velocity in the channel is lower. The total thermal resistance is low for large channel numbers due to high heat transfer rate, and the better temperature uniformity is observed for the larger channel number heat sink. Finally, the effects of the type of coolant on the hydro-thermal performance are also examined numerically. The Nusselt number of the heat sink using GaInSn coolant is larger than that using water.

Effect of boundary conditions on heat transfer and entropy generation during two-phase mixed convection hybrid Al2O3-Cu/water nanofluid flow in a cavity

In this work, the effect of three different boundary conditions on the fluid flow and heat transfer is analyzed for mixed convection in a differentially heated double sided lid-driven square cavity. The current work deals with water-based hybrid Al2O3-Cu/water nanofluid with volume fractions φ ≤ 3%. We use thermal lattice Boltzmann (LB) method to simulate two-phase nanofluid flow for discretely varying Richardson number (0.1 ≤ Ri ≤ 10) at fixed Grashof number of Gr = 104. The experimental and numerical validations of current two-phase LB model show better accuracy in predicting nanofluid behaviour compared to single-phase LB model. Examination of the second law of thermodynamics-based energy efficiency reveals that the heat transfer rate and total entropy generation of the current system are influenced by the change in boundary condition and Richardson number. The addition of nanoparticles is unable to attain desirable effectiveness in the overall improvement of the current thermal system due to augmentation of entropy generation, despite the improvement of heat transfer rate. The current results suggest two different optimal volume fractions based on the maximum heat transfer rate and performance coefficient parameter respectively.

Effect of different frequency functions on ferrofluid FHD flow

Abstract A finite volume method is used to investigate the unsteady thermomagnetic convection of ferrofluid flow in a miniature channel under the effect of constant and oscillating magnetic fields. A magnetic line dipole as a magnetic source is placed under the lower wall of the two-dimensional channel whose lower and upper walls are subjected to a constant heat flux. To generate the oscillating magnetic field, four different frequency functions including rectangle, sine, triangle and sawtooth functions are implemented in the constant magnetic field. The study parameters include four frequency functions, magnetic field intensity as a magnetic number (Mn = 3.833 × 108, 8.624 × 108, 1.533 × 109), frequencies (f = 0.5–5 Hz) and Reynolds numbers (Re = 20–40). Results revealed that applying the constant magnetic field enhances heat transfer and as the Reynolds number increases, the effectiveness of magnetic field on heat transfer rate diminishes. The oscillating magnetic field, regardless of the type of the applied frequency function, improves heat transfer rate due to thermal boundary layer suppression and increase in velocity field. For all applied functions, results show that there is an optimum frequency where maximum heat transfer happens and this frequency increases for higher Reynolds numbers. For rectangle and sawtooth functions with instant change in the magnetic field, two simultaneous vortexes emerges which leads to better heat transfer than sine and triangle functions. The alteration of the pressure drop in one period is proportionate with the shape of the applied frequency even though the range of the alterations reduces with the increase of the Reynolds number.

Review of water-nanofluid based photovoltaic/thermal (PV/T) systems

<span lang="EN-US">Solar energy is secure, clean, and available on earth throughout the year. The PV/T system is a device designed to receive solar energy and convert it into electric/thermal energy. Nanofluid is a new generation of heat transfer fluid with promising higher thermal conductivity and improve heat transfer rate compared with conventional fluids. In this review, the recent studies of PV/T using nanofluid is discussed regarding basic concept and theory PV/T, thermal conductivity of nanofluid and experimentally and theoretically study the perfromance of PV/T using nanofluid. A review of the literature shows that many studies have evaluated the potential of nanofluid as heat transfer fluid and optical filter in the PV/T system. The preparations of nanofluid play an essential key for high stability and homogenous nanofluid for a long period. The thermal conductivity of nanofluid is depending on the size of nanoparticles, concentration and preparation of nanofluids.</span>

Energetic and Exergetic Performances of Plate Heat Exchanger Using Brine-Based Hybrid Nanofluid for Milk Chilling Application

Theoretical study on the energetic and exergetic performances of a counter-flow corrugated plate heat exchanger using hybrid nanofluids for the milk chilling application has been done in the present investigation. Magnesia-silver and Alumina-silver nanoparticles have been dispersed in the ethylene glycol–water mixture and propylene glycol–water mixture (20:80 brine solutions) with different particle volume concentration separately. Effect of particle volume concentration and flow rate of the hybrid nanofluid on the heat transfer rate, convective, and overall heat transfer coefficients, mass flow rate of milk, pressure drop, pumping power, entropy generation rate, second law efficiency, irreversibility, irreversibility distribution ratio, non-dimensional exergy (NDE) destruction, and performance index have been studied. It has been observed that heat transfer rate, convective and overall heat transfer coefficients, pressure drop, pumping power, irreversibility, entropy generation rate, second law efficiency, and milk flow rate increase; while NDE destruction, performance index, and irreversibility distribution ratio decrease with the hybrid nanofluid flow rate and the volume concentration of the nanofluid. Within studied ranges, the hybrid nanofluid yields the maximum improvement of heat transfer rate and convective heat transfer coefficient of about 1.6% and 9.4%, respectively, compared to base fluid. It has also been found that silver + alumina shows slightly better performance improvement and hence hybrid nanofluid is recommended as a suitable alternative for the milk chilling units.

Erosion-corrosion effect of nanocoolant on actual car water pump

In automobile cooling system, water and ethylene glycol are usually used as coolant. For many years, nanofluid has been reported to enhance thermal properties of conventional heat transfer fluid due to dispersion of solid particles which exhibit superior thermal conductivity. Many past researchers found improvement of heat transfer rate in automobile cooling system by using nanofluid as coolant. However, there are very few reported on drawback such as tribological impact on components in automobile cooling system. Hence, this paper focused to determine erosion-corrosion effect of nanofluid on aluminium impeller in Perodua Kancil D37 water pump. Working parameters such as inlet pressure, coolant temperature and rpm of pump were in line with ASTM D2809-09 standard. Testing coolants were made up of corrosive water, ethylene glycol and graphene nanoplatelets. Each pump surface profile was inspected using 3D imaging microscope after undergoing 100 hours of testing continuously. Also, precise weight measurement was carried out before and after testing to determine total material loss. It was observed that corrosion effect was about the same for both base coolant and nanocoolant. Erosion-corrosion effect increased material loss when nanocoolant was used instead of base coolant. Based on ASTM 2809-09 standard, erosion-corrosion damage on impeller was found to be minimal and scored high rating in evaluation. Thus, both coolants can be considered to be incorporated in future cooling system.

Use of MWNTs‐COOH to improve thermal energy storage and release rates of capric–palmitic–stearic acid ternary eutectic/polyacrylonitrile form‐stable phase change composite fibrous membranes

A series of novel capric–palmitic–stearic acid ternary eutectic/polyacrylonitrile/carboxyl purified multi‐walled carbon nanotubes (CA–PA–SA/PAN/MWNTs‐COOH) form‐stable phase change composite fibrous membranes (PCCFMs) were fabricated by electrospinning and physical absorption methods. In these form‐stable PCCFMs, the CA–PA–SA ternary eutectic was served as phase change material for thermal energy storage, and the loaded MWNTs‐COOH was acted as thermal conductivity enhancement filler to improve heat transfer rates, as well as electrospun PAN/MWNTs‐COOH fibrous membranes with different weight fractions of MWNTs‐COOH (i.e., 5, 10, and 20 wt%) were used as supporting materials to provide structural strength and prevent liquid leakage of melted CA–PA–SA ternary eutectic. The morphological structure and thermal performances were investigated and analyzed. The images of scanning electron microscopy showed that the CA–PA–SA ternary eutectic was uniformly embedded and dispersed into the three‐dimensional porous network structure of electrospun PAN/MWNTs‐COOH fibrous membranes. Thermal performance tests suggested that the melting and freezing times of the CA–PA–SA/PAN/MWNTs‐COOH form‐stable PCCFMs with the addition of 10 wt% MWNTs‐COOH were significantly shorten by about 52% and 56% in comparison with those of the CA–PA–SA/PAN form‐stable PCCFMs. Their phase change temperatures and enthalpies were about 7°C–32°C and 130–138 kJ/kg, respectively. POLYM. ENG. SCI., 59:E403–E411, 2019. © 2018 Society of Plastics Engineers

On Darcy-Forchheimer squeezed flow of carbon nanotubes between two parallel disks

Purpose The purpose of this paper is to construct mathematical model for squeezed flow of carbon-water nanofluid between parallel disks considering Darcy–Forchheimer porous medium. Thermal conductivity of carbon nanotubes is estimated through the well-known Xue model. Such research work is not carried out in the past even in the absence of Darcy–Forchheimer porous space. Forchheimer equation is preferred here to account for both low and high velocity inertial effects. Researchers also found that dispersion of carbon nanotubes in water elevates the thermal conductivity of resulting nanofluid by 100 per cent. Design/methodology/approach Homotopy analysis method (HAM) is used for the convergent series solutions of the governing system. Findings Nusselt number at the lower disk increases when squeezing parameter Sq enlarges. This illustrates that heat transfer rate at the lower wall can be enhanced by increasing the squeezing velocity of the lower disk. The results demonstrate a decreasing trend in temperature profile for increasing volume fraction of carbon nanotubes. Moreover, improvement in heat transfer rate because of existence of carbon nanotubes is also apparent. A significant enhancement in temperature profile is depicted when inertial permeability coefficient is enhanced. Skin friction coefficients at the lower and upper disks are higher for MWCNTs in comparison to the SWCNTs. Originality/value To the best of author’s knowledge, no such consideration has been given in the literature yet.

Flow and Heat Transfer Investigation of Forced Convection of Nanofluid in a Wavy Channel at Different Wavelengths and Phase Difference

Changing the fluid properties and flow geometry are two common ways of making an improvement in heat transfer rate. Recent investigations on nanofluid, as such suspensions are often called, indicate that the suspended nanoparticles remarkably change the transport properties and heat transfer characteristics of the suspension. Bending walls can also improve heat transfer by increasing the total heat transfer surface and changing the behavior of the flow. In this work a two dimensional incompressible laminar nanofluid flow in a wavy channel with sinusoidal curved walls is numerically investigated. The finite volume method, and Rhie and Chow interpolation with a collocated mesh are used for solving the governing equations. The effects of the volume fraction of nanoparticles, Reynolds number, the wavelength, Phase lag and amplitude on the heat transfer rate are studied. The present work showed good agreement with existing experimental and Numerical results. Increasing the amplitude of the wave and nanoparticles volume fraction, and decreasing wavelength of the wave, has great effects on enhancement of heat transfer rate.

Horticultural packaging systems of the future: improving reefer container usage

Large quantities of fresh produce, such as pome fruit, are exported every year to international markets across the world using refrigerated freight containers (RFC). However, the current packaging systems typically employs 1.2×1.0 m pallets, which leave about 10% of the RFC unused. The introduction of an improved packaging system that better utilises RFC volume and improves the cooling efficiency could enable a significant reduction in transport costs, carbon emissions and postharvest losses. This study therefore investigated two new packaging systems under forced-air cooling (FAC; horizontal airflow) and RFC (vertical airflow) conditions using computational fluid dynamics. The Tes packaging system consists of a novel pallet and carton design, which occupies 98.9% of the RFC floor area. The Hex packaging system, on the other hand, uses an isosceles trapezoid carton. The complimentary Hex pallet results in a 97.4% RFC floor area usage. For FAC, the Hex design had a reduced heat transfer rate (10%) compared to the standard (STD) design. Conversely, compared to the STD design, the Tes packaging system improved heat transfer rate by 6%. Overall, both the Hex and Tes packaging system are feasible designs. The lessons learnt in the conceptual study can guide future studies to further develop packaging systems that improve the RFC usage and cooling efficiency.

Convective heat transfer enhancement in a pitted microchannel by stimulation of magnetic nanoparticles

Convective ferrofluid heat transfer in a microchannel under static (SMF) and rotating magnetic fields (RMF) has been investigated. The microchannel has a cylindrical pit in which a heat source with a constant heat flux is applied on the bottom wall. The top wall of pit is positioned next to a rotational permanent magnet that creates RMF, while it is stationary for SMF. The heat transfer characteristic results at various flow rates, magnetic field inductions (B) and nanoparticle volume fractions (ϕ = 0.1–2%) by applying RMF have been compared to those of SMF. Results depicted that using ferrofluid results in improvement of heat transfer rate compared to DI-water. However, applying SMF causes to reduction in the heat transfer characteristic. Results illustrated that RMF is more effective compared to SMF. In RMF, the influence of B and rotational speed of magnet (W) have been considered; heat transfer characteristics enhanced by increasing B and W. The effect of W more than 18 rad/s is not significant. The effect of increase in ϕ on heat transfer coefficient is also evaluated and increasing trend is observed. Maximum value of heat transfer coefficient is achieved for RMF with B = 1100 mT, W = 18 rad/s and MNPs concentration of 2%.

Development of a New Correlation and Post Processing of Heat Transfer Coefficient and Pressure Drop of Functionalized COOH MWCNT Nanofluid by Artificial Neural Network

Background: Because of nanofluids applications in improvement of heat transfer rate in heating and cooling systems, many researchers have conducted various experiments to investigate nanofluid's characteristics more accurate. Thermal conductivity, electrical conductivity, and heat transfer are examples of these characteristics. Method: This paper presents a modeling and validation method of heat transfer coefficient and pressure drop of functionalized aqueous COOH MWCNT nanofluids by artificial neural network and proposing a new correlation. In the current experiment, the ANN input data has included the volume fraction and the Reynolds number and heat transfer coefficient and pressure drop considered as ANN outputs. Results: Comparing modeling results with proposed correlation proves that the empirical correlation is not able to accurately predict the experimental output results, and this is performed with a lot more accuracy by the neural network. The regression coefficient of neural network outputs was equal to 99.94% and 99.84%, respectively, for the data of relative heat transfer coefficient and relative pressure drop. The regression coefficient for the provided equation was also equal to 97.02% and 77.90%, respectively, for these two parameters, which indicates this equation operates much less precisely than the neural network. Conclusion: So, relative heat transfer coefficient and pressure drop of nanofluids can also be modeled and estimated by the neural network, in addition to the modeling of nanofluid’s thermal conductivity and viscosity executed by different scholars via neural networks.

Numerical investigation of the effects of fin shape, antifreeze and nanoparticles on the performance of compact finned-tube heat exchangers for automobile radiator

In this paper, heat transfer and pressure drop of air in the radiator of an internal combustion engine automobile were investigated. First, three types of fins including louvered, triangular vortex generator and rectangular vortex generator were modeled and their performance were compared with a plain fin. Effects of adding antifreeze in volume ratios of 40, 50 and 60% on the performance of louvered and rectangular vortex generator fins were investigated. Finally, the effects of adding copper oxide and aluminum oxide nanoparticles on the heat transfer improvement of louvered and rectangular vortex generator fins were simulated. The results demonstrated that louvered fin had the highest heat transfer rate compared to the other fins and improved it up to 24.6% in comparison with plain fin; however, its air side pressure drop increased 67.7%. Adding antifreeze resulted in a decrease in heat transfer rate. For example, heat transfer rate decreased for louvered and rectangular vortex generator fins at 60% vol. antifreeze, 12.9 and 11.8% compared to pure water, respectively. Also, adding copper oxide and aluminum oxide nanoparticles improved heat transfer rate and compensated harmful effects of antifreeze and it increased heat transfer rate in comparison with pure water.