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Rapid depletion of fossil fuels and escalating crude oil prices led the researchers to ascertain alternative feedstock as a substitute for mineral diesel. Biodiesel produced from non-edible sources was one among them. In the present investigation, palm stearin wax, a residue of palm oil extraction was used as a value-added feedstock for the production of biodiesel. Palm stearin biodiesel (PSBD) was derived from this feedstock using single stage transesterification process involving methanol and sodium hydroxide as a catalyst. PSBD was blended with mineral diesel at 20% (D80PSBD20) and 50% (D50PSBD50) in volume basis. The effect of variable compression ratios on the performance and emission phenomena of direct injection CI engine was analysed for test fuel blends. The tests were carried out for compression ratios 17:1, 17.5:1 and 18:1. Among all the fuel blends, D80PSBD20 blend showcased better performance characteristics along with reduced exhaust emissions at compression ratio of 18:1.

In this research work, the characterization of the palm stearin biodiesel was made using Nuclear Magnetic resonance (NMR), Fourier transform infrared spectroscopy (FITR) and GC/MS methods. Analysis of the composition of fatty acids was done using the GCMS apparatus based on the retention time. Fourier transform infrared spectrometer was used for the spectrum analysis of the various functional groups and bands located in it. The properties of the palm stearin biodiesel were predicted adopting the American Society for Testing and Materials (ASTM) standards. Measured values of the properties were the density at 18°C as 0.88 g/m3, kinematic viscosity at 35°C as 3.4 mm2/s, the calorific value of the palm stearin as 37121 kJ/kg and the flash and fire points of the biodiesel as 130°C and 160oC respectively. The rapid and correct characterization of the palm stearin biodiesel was made by the NMR.

Wind speed reaches in the range between 100kmph to 200kmph during cyclone causing severe damages to the power supplying utility pole which is to be replaced. It is observed that the stresses acting on the existing pole design (i.e., tapered rectangular) is high and increasing the cross sectional area of the pole reduce the stress induced and hence hexagonal cross section is chosen. The structural analysis is carried out using ANSYS finite element code. Apart from the existing pole design, tapered hexagonal pole and novel stepped hexagonal pole of identical dimensions are chosen. The material chosen for the electric pole is PCC for a wind speed of 200kmph. Load and the maximum stress acting on the novel stepped hexagonal shaped electric pole is found to be lesser compared to other designs. The deformation of the stepped hexagonal shaped electric pole is also less. The pole design is verified analytically and the factor of safety of the stepped hexagonal shaped pole is found to be more than the prescribed requirement and the design is found to be safe. Thus, the stepped hexagonal shaped pole can be used as a utility pole in the cyclone prone areas.

Wind energy is clean form of energy which is abundantly available. A great deal of study has been carried out lately in order to utilize the wind energy available on a large scale as it does not affect the environment and it is a sustainable source of energy. The modelling and simulation of wind turbine system supports mainly in improving the design and performance of the wind turbine. In the past few years, MATLAB©-Simulink© became one of the most common software, which is important for modelling, and simulation of dynamic systems. The use of MATLAB© in modelling and simulation of dynamic real-world systems is unprecedented. As the MATLAB© provides graphical interface, it gives clear picture about the performance of wind turbine in a real-world scenario and model accordingly. In this study, a horizontal axis wind turbine with variable pitch mechanism is considered and simulated it in MATLAB©-Simulink© by varying the wind speed and pitch angle. The active power output of the turbine varies with the wind speed and the angle of attack (β). Based on the results, it is found out, the optimum characteristics of wind turbine like pitch angle and turbine speed is obtained at various wind speed. Therefore, by simulating and analysing the results, it is found out that the maximum active power output of the turbine is achieved at the optimum pitch angle.

In the present experimental investigation, jojoba biodiesel-diesel bends were fuelled to a four stroke single cylinder compression ignition engine at compression ratio of 17.5 to understand its emission and performance phenomenon. Jojoba biodiesel was prepared through base catalysed transesterification process using NaOH and methanol. The physio-chemical properties like calorific value, kinematic viscosity, density, flash and fire point were determined and found to be within ASTM standards. The performance parameters includes brake thermal efficiency, brake specific fuel consumption and emission parameters includes unburned hydrocarbon, carbon monoxide, oxides of nitrogen and smoke were assessed. Optimal operating parameters of the engine was analyzed by incrementing and decrementing the compression ratio upto CR18 and CR17 respectively.

Technology has developed to far greater heights than ever before resulting in many lives being dependent on them. One such case is the physically disabled people. The motion of physically disabled people who required support for moving on different terrains can be made independent with the help of a wheel chair using a rocker bogie mechanism. Rocker boogie mechanism is a suspension system that can climb obstacles having size twice the diameter of the wheel and also is less complicated compared to other suspension systems. Commercial finite element code, ANSYS is used to analyze the wheel chair using rocker bogie mechanism. Static structural analysis is performed and the parameters like hydrostatic pressure, total deformation, and normal stress is analyzed. The parameters are found to be within the acceptable limits and the design is found to be feasible.

Analysis of the Moderate and Intense Low-Oxygen Dilution (MILD) combustion burner is performed using commercial CFD code ANSYS. The burner is designed in such a way to be a non-premixed and open burner. Four exhaust gas recirculation (EGR) pipes are used to transport part of the exhaust gas from exhaust to the inlet where it is mixed with the fresh oxidant. The chamber temperature distribution of MILD combustion chamber is found to be reduced in comparison with normal burner with conventional combustion. This leads to reduction in the exhaust gas temperature at the MILD combustion burner outlet and reduces the NOx emissions.

The focus of this study is to improve the mixing at the exit of supersonic jet and estimate the decay of total pressure and Mach number by introducing interior grooves on top and bottom side alongside the divergent length of the convergent divergent nozzle. Geometrical model of the nozzle is created using CATIA software and analysis is performed using ANSYS. The decay of the total pressure and Mach number is studied for over expansion (4 bar), optimum expansion (6 bar) and under expansion (8 bar) instances by fixing Mach number at exit of the nozzle as 1.8 for nozzle configurations with and without inside grooves. The grooves act as passive controls ensuing significant enhancement of jet mixing. The decay of Mach number and total pressure alongside the jet centreline axis is greater for grooved nozzle in contrast to plain nozzle. The centreline axis total pressure decay comparison shows semi-circular grooved nozzle decays 30% faster than the plain circular nozzle, whereas square grooved nozzle decays 62% faster than the plain circular nozzle in under expansion condition. The characteristics of decay increased with increase in groove length.

As the construction of Savonius rotor is simple, the performance of Savonius rotor is poor. This can be enhanced by modifying either the shape of the blade and/or number of blades. In this work, modifications are adopted in both shape and number of blades. Numerical investigation is carried out using commercial code ANSYS©. A comparative study is carried out on the multi bladed Savonius rotors with different blade configurations, namely two bladed (simple), three bladed and four bladed Savonius designs. Modified Bach type rotor is also considered based on the shape of the blade. Among all the configurations, the modified Bach type rotor gives the best performance characteristic in terms of coefficient of power (Cp) and coefficient of torque (Ct). However, it is observed from the simulation that the four bladed Savonius rotor give the poor performance compared to the two bladed and three bladed Savonius rotors.

A land and water capable vehicle floats on the water surface and its versatility isn't constrained by the depth of water channel. For most submerged land vehicle (SLV), water activities are restricted to fording. In this paper a current SLV has been inspected as far as land and water capable abilities are concerned. This being a relatively new field, the conduct of the submerged land vehicle during amphibious operation is as yet very little publicised. Subsequently during underwater fording the dynamic forces that act up on the SLV are obscure. These powers legitimately impact and influence the strength of the SLV submerged. In this manner there is a need to examine the stream around the SLV. The CFD examination is generally used to study about the conduct of items submerged in non-static liquids. It means to decide how proficiently a vehicle can travel through the medium and how liquid stream and vehicle movement influence each other simultaneously. In the present situation when the SLV is moving submerged, the liquid isn't restricted between wall type conditions, for example, pipes or bound stream cases. The liquid is allowed to move around the item and connect just with its outside “wet” layer. This suggests it is the stream including the body shape that must be considered. By evaluating the weight and speed scattering around the SLV, made by the opposition of the fluid, we can choose the various forces acting on the SLV in different planes and concentrate the stream dynamic steadiness of the SLV when it is encountering deep fording.

Fusion Deposit Modeling (FDM) is a 3D Printing method which builds layer–by-layer of a component by the melting and deposition of plastic through the moving nozzle. Any complex shape which is not possible by convention fabrication technique can be fabricated using this technique. Moreover, this technique allow the innovator to develop the prototype much faster than the convention method. The complex shape prototype that chosen in this work is the radial flow centrifugal pump and it is the most common and widely used kinetic energy pump. The digital model of the centrifugal pump was prepared using the solidworks. The different component of the centrifugal pump like impeller, casing, suction and shaft also modeled and assembled. The design details of the impeller of the pump and casing is arrived after careful design calculation and it is prepared in such a way to have more efficiency of converting energy in the impeller. The impeller blades, shape, number of blades are arrived based on the total head and discharge. These impeller, suction, casing and shaft all are fabricated by using the FDM of 3D printer using ABS Plastic. The design plays a major role in preparing the centrifugal pump impeller and other components. The fabricated component should be matched accurately while assembly. Moreover, the components fabricated using the rapid prototyping solve the purpose when compare to the other conventional methods. Moreover this FDM technique is successfully benefited in manufacturing light weight prototype, tooling and creating customized design. However, the quality of prototype developed through this technique is relatively lower than the other formative or subtractive technique. This challenges in this technique is addressed by analyzing the microscopic structure of the ABS plastic and presented in this paper.

Piezoelectric tiles can be used to generate electricity but its sturdiness to withstand any applied load is a major concern. The material should withstand all types of loadings. Therefore, the focus of this study is to analyze the withstanding ability of the piezo tile by considering different piezo tile materials tested under different loading conditions. Two materials namely, structural steel and carbon fiber is selected as tile materials which is subjected to uniform distributed load and non-uniform distributed load conditions. Finite element method is chosen to carry out the analysis using commercial finite element code ANSYS. The static structural properties namely, total deformation, equivalent (von-misses) stress and equivalent elastic strain is compared for both these materials tested at different loading conditions. Based on the parameters, the structural steel is observed to the apt material for fabrication of piezo tile used for tapping power from footsteps.

The focus of this study is to analyze the static mechanical properties of the helical Savonius vertical axis wind turbine blade. Commercial finite element code ANSYS is used to perform the static structural analysis. The helical Savonius wind turbine blade is tested by force varying from 15 N to 25 N representing the wind conditions ranging from 5 m/s to 11 m/s. The properties namely, maximum principal stress, equivalent (von-misses) stress, shear stress, maximum shear stress, equivalent elastic strain, and total deformation are analysed. The various static mechanical properties are observed to be the maximum for wind load of 15 N. The outer edges of the helical Savonius vertical axis wind turbine blade is observed to have the maximum total deformation values and the prolonged use of the helical Savonius wind turbine blade will lead to damage along the outer edges of the turbine blade leading to failure of the wind turbine blade.

The focus of this study is to understand the combustion and evaporation characteristics of organic gel fuels. Fuels made by using chemicals such as triethanolamine, kerosene, glycol, and ethanol along with gelling agent, methylcellulose. Different mixtures of triethanolamine and kerosene are tested to know the exact proportion at which these two chemicals were mixable. The composition is estimated to be 90% triethanolamine and 10% kerosene. Kinematic viscosity, flash and fire points, contact angle are estimated for various test fuels and gel. Droplet evaporation tests conducted at room temperature and at 100℃ revealed the change in diameter ratios and helped in understanding the evaporation characteristics of different test fuels and gel. Glycol gel evaporates very easily and the process lasted only few seconds. At high temperature, glycol gel evaporated faster compared to other tested chemicals.

Thermal load due to non-uniform temperature variations is one of the reasons for premature exhaust valve damage. Thermal analysis helps in estimating the heat flow accurately so that temperature distribution can be lowered / optimized to prevent failures due to excessive stresses. Therefore, the focus of this study is to perform thermal analysis on the compression engine exhaust valve at steady state condition. The investigations are carried out using ANSYS. Three different materials, namely aluminum nitride, stainless steel, and silicon nitride are chosen. Silicon nitride materials is found to be the right material for engine exhaust valve on the basis of material mechanical properties and thermal distribution related thermal stress induced on the exhaust valve.

As the fossil fuel reserves are getting depleted, the focus is towards alternative fuels to meet the future energy demand. Literatures showed that 20% biodiesel blend will be more appropriate in diesel engine without engine modifications. Few researches are performed on varying the compression ratio to understand the combustion behavior. The focus of this study is use understand the combustion behavior by varying compression ratios using third grade sesame oil. The blended fuel (B20) and its fuel properties are found to be within the stipulated standards. The in-cylinder pressure increases as the compression ratio is increased. Also, the rate of pressure rise and rate of heat release is higher as the compression ratio is increased. This confirms the fact that blended sesame biodiesel can be used as an alternate fuel source for diesel at higher compression ratio (18:1).

A vehicle suitable for land and/or water touches the surface of the water and its portability is not limited by depth. For most land vehicles (SLV), water tasks are limited to wading. In this article, we will complete a review of an SLV which is one of the most widely created after the Second World War and used worldwide by a large number of nations. Being an initial field, the behavior of the land vehicle lowered during a deep advance is still very little exposed. As a result, during deep gain, the dynamic powers following SLV are obscure. These powers legitimately affect and influence the strength of the submerged SLV. In this sense, it is necessary to examine the sequence around the SLV. However, since the progress of the lowered land vehicles is excessively expensive and the assembly of several models is limited, it is not possible to reproduce the test sequence in a full-scale model committed in the finishing phase of the structure. As a result, circumstances require studies that use cheaper recreations that offer the opportunity for different test conditions. This article presents a progression of measures dependent on client inclination for their sort and portability, to portray the cross-country execution of military vehicles. Gauges were taken from existing vehicles, so they are handy.

The focus of this study is to perform structural analysis on the cross flow vertical axis wind turbine using finite element code ANSYS. Two different materials, namely aluminium alloy 2024 and magnesium is chosen. The wind turbine is tested for two different applied force namely 26.16 N and 13.08 N obtained based on the wind velocity (4 m/s to 10 m/s). These materials are chosen as it is lighter in weight and possess higher strength. The static mechanical properties of these materials used for making cross flow wind turbine are investigated and the properties namely, maximum principal stress, equivalent stress, total deformation, equivalent elastic strain and maximum principal elastic strain are plotted. The maximum principal elastic strain and total deformation of magnesium material based cross flow turbine is almost negligible compared to aluminium alloy based wind turbine. The maximum principal stress as well as equivalent stress induced in magnesium material based cross flow wind turbine is lesser by nearly 175% and 100% respectively. Therefore, magnesium material is found to be the suitable material that can be used for fabricating cross flow wind turbine.

The focus of this study is to analyze the behaviour of a stiffened composite panel. Two different curved panels with ‘Z’ section and angle section stiffeners are used. Stiffeners are single moulded with the panels instead of fixing and it is used to minimize the deformation. This configuration is used to avoid the de-lamination of stiffeners from the panel. The materials used are carbon fiber and glass fiber and the fiber used in this study are unidirectional. The lateral axis of the panel is fixed supported and the longitudinal axis of panel (or the longitudinal axis of stiffener) is subjected to various compressive loads ranging from 5kN to 100kN. Buckling test is made to predict the buckling capacity of the material. Finite element analysis is done using ANSYS_LS-DYNA workbench. The variations in total deformation, nominal stress and shear stress with respect to loads are plotted. The buckling strength is more for carbon fiber than glass fiber. Carbon fiber can be stretched more as the stress distributed in carbon fiber is more than glass fiber. Glass fiber will break before carbon fiber as the shear stress in glass fiber is high.

Lot of effort is made to reduce the fuel consumption by automobile vehicles and this can be achieved by reducing the mass of the automobile vehicles. Leaf spring widely used in all types of vehicles including electric vehicles is one such component which could be attempted. Three different materials namely conventional steel, glass epoxy composite and hybrid composite (combination of both steel and glass epoxy) are considered for the leaf spring. FEA analysis is performed using ANSYS finite element code. Von-Misses stresses, deformation, principal stresses and strain are the main parameters that are considered in this study for different loading conditions. The mass of hybrid composite material is 34% lesser compared to conventional steel. Maximum principal stresses of hybrid composite material are 60% lesser than steel. The mass of hybrid composite material is 34% lesser compared to conventional steel. Finally, the hybrid composite material can be used as a leaf spring material thereby reducing the overall weight of the automobile vehicles.

Additive manufacturing is emerging as a preferred approach to manufacture complex three dimensional components easily within a short span of time. In this study, cross axis wind turbine blades and its components are produced using fusion deposition modeling using Acrylonitrile Butadiene Styrene (ABS) material. The 3D CAD models are converted into .STL file which are processed further in “Slicer” freeware software. This convert the model into series of thin layers and creates G-code file which acts as an input to automated 3D printing machine to lay layers of loaded thermoplastic material successively to build the model from series of cross sections. The components produced by additive manufacturing is assembled and the obtained cross axis wind turbine (CAWT) is investigated using an open jet wind tunnel for wind velocities varying from 4 m/s to 10 m/s. The dimensionless performance parameters i.e., coefficient of power (Cp) and tip speed ratio (λ) are plotted. In general, the Cp value of CAWT increases gradually and reaches the maximum value around λ = 1.20. A maximum Cp value of 0.02385 is observed for wind velocity Vα = 10 m/s. Thus, the 3D printed components by additive manufacturing can be used to produce small wind turbines.

The growing truck industry, results in larger fleet of trucks serving various transportation needs of the society. On the flip side, the increased sale of vehicles causes environmental pollution affecting the fragile ozone layer. Government and regulatory bodies across the globe enforced tough emission measures to curb the menace. The tougher emission norms translate into design challenges for the truck OEM’s to design lightweight and complex radiator to meet higher operating pressure and durability cycle targets within a tight packaging vehicle space. Robust radiator design is the need of the hour to address the design challenge. A robust design approach coupled with traditional nominal analysis is proposed to determine robust radiator design insensitive to variations. Fatigue Assessment also included in the approach. Nominal design analysis shows that nominal deformation and stress response has 49% reliability and 51% unreliability, which indicates that nominal design does not factor in the variations occurring due to assembly, raw material and manufacturing process. The proposed robust approach identifies robust radiator designs less sensitive to uncertainty and shows 95% reliability. Robust design has 5x higher pressure cycle life as compared against the nominal design. The robust design concept having higher reliability and less sensitive to variations are identified. The approach highlights that robust design has higher pressure cycle durability as compared against the nominal radiator design. Better fatigue life estimation is obtained by using pressure cycle test results.

The focus of this study is to carry out stress analysis of the connecting rod of compression ignition engine using finite element method. Commercial finite element code ANSYS is used to perform this investigation. Four different materials viz., A356, A356-5%SiC-10% Flyash stir cum squeeze casting, A356-5%SiC-10% Flyash stir casting, and Al2024-T3 is selected for the connecting rod. Static structural mechanical properties namely, total deformation, equivalent elastic strain, and equivalent (von-misses) stress is calculated. A356-5%SiC-10% Flyash stir cum squeeze casting material gives the lesser total deformation, equivalent elastic strain and equivalent stress values among all the tested materials. Total deformation of A356-5%SiC-10% Flyash stir cum squeeze casting material is reduced by 38.50% in comparison with base material (A356). Moreover, the equivalent stress distribution of A356-5%SiC-10% Flyash stir cum squeeze casting material is nearly same with the base material (A356).

Weight reduction of about 100 kg in an automobile decreases the fuel consumption of about 0.7 L for every 100 km of traveling is the reasoned fact that many research are fielded towards conversion of metal to plastic. This was the main idea for executing this project i.e. replacement of wheel housing of a four-wheeler from metal to plastics. Sheet molding compound (SMC) is the material selected for this conversion project. The designing of the wheel housing was carried out using the Pro-e software with actual dimensions. The effectiveness, reliability, durability and the strength was analyzed using the ANSYS software. It was noted that the deflection of the material during the application of maximum load was 0.42 mm and the stress developed at the same time was noticed to be 39.008 N/mm2 which was within permissible limits. Based on the outcomes, SMC could be viable replacement for the metal wheel housing.

Bayesian regularized Artificial Neural Network (ANN) coupled with genetic algorithm was used to develop a model to predict the optimized process variable parameters for the transesterification proc...

The current study aims to give a detailed literature review in a dental implant material. This paper is focusing on titanium implants, popular zirconia implants, and PEEK biomaterial. Major topics includes material science and the importance of PEEK material. This involves both transplant materials and mechanical and bio properties. Titanium plays a vital role in the implant industry as it has very good physical properties. Zirconia materials and PEEK prove to be promising in the future. The suitable selection of implant biomaterial is an important factor for good dominance and success of the implant. The biological human system does not accept any material. This study will try to finalize various bio-material which were used in the transplant industries.

The lifeline of dental embedding is reliant on thread design and bone eminence. This work helps to explore the outcome of different thread plans in the transplant. The role of transplant thread design plays a dynamic part to promise transplant steadiness. Buttress thread design established for transplant and geometrical data are consistent. The mandibular molar area was measured and supercilious it to be isotropic and homogeneous. Modeling of the transplant done by Solid Work. Perpendicular masses of 100 N were placed and stress circulation was premeditated. Stress attentiveness was understood laterally the mesiodistal trail connected to the buccolingual track. The cortical jawbone near the cervical section of the transplant and the cortical jawbone following the primary thread design of the transplant practiced the highest stress attentiveness. The outcomes express the submission of thread outlines at various grades of osseointegration needed an important result on the stress circulation outlines in the adjacent thin shape.

Governmental agencies across the globe are constantly evolving with stringent emission laws to tackle the problem of CO2 and NOx/SOx emissions. New emission standards force the Truck OEM’s to redesign the engine. The paper is aimed to measure the header tube joint stress of the radiator subjected to random variations in geometry, shape and material properties. Linear analysis will not consider the uncertainty and randomness due to tolerance, process changes, part-part variation etc. Stochastic finite element analysis (FEA) is carried out to account the uncertainty in the system. The finite element model of radiator system is built and baseline linear simulation is performed to obtain the baseline deformation and baseline stress responses. Then the uncertainty and random variation due to the geometry, material and shape variable is defined by a normal distribution function. Random designs are generated by defining the upper and lower bound limit values for the input design variable. Random designs are populated using Monte-Carlo simulation technique. 250 random design points are created for each design variables. Then stochastic simulation is performed to evaluate the responses at random design points. Statistical and probabilistic tools are used to post process the simulation results. The paper showcases application of stochastic simulation method which aids in indentifying the robust design with minimum variations. This also enables engineers and designers to understand the relationship and significance between different design variables in designing energy efficient systems.

The main function of the gearless transmission system is to transmit power between two shafts through the sliding links that develop revolute pair between the hubs of two shaft. Normally the output link is bent at any angle between 0 and 180°. Moreover, as the hub in the driving shaft rotates, holes in this hub rotate, which in turn pushes the links and it drive the output. Moreover, torque developed in the small wind turbine is small so it is effectively used in this low torque applications. The objective of this project is to analysis gearless drive that is being simple and transmitting power preciously at almost right angle without any bevel gears. This mechanism is completely analysis using Ansys© software to lookout the elbow rod the hub under different working condition. Numerical analysis is made by rotating the mechanism at different rpm, viz. 0–150 rpm. Reaction forces and reaction moment are analyzed for 5 s simulation and compared with allowable stress. In this investigation, the effect of number of links and size of link is studied to find the permissible operating speed of mechanism. The major outcome of this work is to get the permissible limit of the stress, strain, speed, torque transmitting capacity of this mechanism as it is very much attracting the research community in replacing the conventional bevel gears. It is observed that the optimum number of link for better transmission is 8 and its diameter is 8 mm, and optimum speed of the mechanism is 100 rpm, so this mechanism is suitable for the small wind turbine.

The thermal performances of shell and tube heat exchanger [STHE] are investigated using Ag–W and CuO–W nanofluids with suspended particle volume concentrations between 0.02% and 0.06% of Ag and CuO. The comparison is made with reference to base fluid. The result revealed that thermal conductivity of the nanofluids, which is dependent on the particle volume concentration, influenced the heat transfer ability. Highest overall as well as convective heat transfer coefficients and highest actual heat transfer are obtained for 0.06% volume concentration CuO–W nanofluid. An improvement of about 19% in heat transfer coefficient is recorded for 0.06 vol% of CuO–W nanofluids with respect to water. Also, the overall heat transfer coefficient enhanced between 64 and 79% for 0.06 vol% of CuO–W nanofluids. However, in the tube-side, pressure drop increases with increase in nanofluid volume concentrations. Actual heat transfer improved by 39–56% with reference to water. It can be concluded that better heat transfer characteristic for the STHE is obtained by keeping the shell-side mass flow as fixed and varying the tube-side mass flow rates.