In this study a plate-Fin heat exchanger (PFHE) with offset-strip fins has been optimized on air-air, water-water and air-water working fluids types. In the first step - designing the PFHE - the heat transfer and pressure drop analyses were done. Considering the geometrical parameters of fins (pitch, height and offset length of fins) and the relationship of the amount of heat transfer and pressure drops with the velocity of working fluids in each types, the volume of PFHE and its total annual cost based on the allowable pressure drop on both sides as the constraints were calculated. Then, Genetic Algorithm (GA) was used for searching and optimization of the structure sizes of the PFHE considering pressure drop constraints. Comparing the current results with the literature shows that the volume of optimized PFHE for all three types decreases from 10 to 15% and the total annual cost declines from 5 to 25%.

heat transfer is one of the most critical processes in the industry, and by increasing the efficiency of the heat exchanger, energy consumption of systems will be reduced. Very tiny particles in nanoscale dimensions, when uniformly dispersed and stably suspended in the base fluid, efficiently improve the thermal properties of the base fluid. With the help of nanofluids, the heat transfer rate increase. The purpose of this research is to investigate the thermal and hydraulic characteristics of nanofluid in turbulent flow regime in a plate heat exchanger with a sine pattern in which cold and hot flows alternately pass through the plates. First, problem geometry is modeled and simulated in ANSYS-FLUENT software. All properties of nanoparticles are dependent on temperature, velocity, and particles diameter, and are added to software in the form of a separate code. Simulations are for different parameters such as wavelength to amplitude ratio (L/A), Reynolds number, volume fractions of nanoparticles and nanoparticle diameter. The results indicate that the best shape of the wave for the highest heat transfer rate in the heat exchanger is gained for equal wave amplitude and wave length.

In the present study, the hydraulic-thermal design and optimization of a gasketed-plate heat exchanger (GPHE) with an objective function of heat exchanger performance index (the amount of transferred heat exchange to pumping power ratio) is carried out. This process is made by considering 6 design parameters (the port diameter, plate thickness, the enlargement factor, the compressed plate pack length, the horizontal port distance, and the vertical port distance) and through the Bees Algorithm (BA). The present study achieved three solution sets for the design parameters by investigating the sensitivity of the design parameters heeded in the optimization of the GPHE. The design parameters in these three optimal solution sets were opted for in such a way that heat transfer increased by 41. 6%, 34. 55%, and 20. 7%, and pressure drop decreased by 11. 89%, 27%, and 83%, respectively.

This article reports an experimental study of heat transfer characteristics of multi-walled carbon nanotubes (MWCNTs). These nanofluids, consisting of water with different weight concentrations of nanofluid (0. 0. 1–,0. 145% wt. ), were flown in counter flow plate heat exchanger under turbulent conditions (2500 < Re < 6500) for cooling applications. The nanofluid was prepared by dispersing MWCNT nanoparticles in the presence of sodium dodecyl sulfate (SDS) and water as base fluid. The results showed that the convective heat transfer coefficient (HTC) of nanofluid was higher than that of the base fluid at an equal mass flow rate and inlet temperature. The heat transfer coefficient of nanofluid increased by mass flow rate and temperature rising. Also, the heat transfer coefficient and the concentration of MWCNTs nanofluid showed a positive association at the same temperature. At a constant weight concentration, the heat transfer coefficient increased when the Reynolds number increased. The slope weight concentration tends to rise as the heat transfer coefficient grows. The increase in Reynolds numbers (or mass flow) was less than the increase in the concentration of carbon nanotubes. According to the performed experiments and software analysis (QUALITEK 4), the heat transfer coefficient and concentration are both manifolded at the same time. But there was an inverse correlation between the heat transfer coefficient and flow rate.

In the present study, turbulent flow in channels of a plate heat exchanger with corrugated Chevron plates has been simulated numerically using the commercial CFD package, FLUENT. 3D models of common corrugated Chevron plates with Chevron angles of 45-45 and 60-60 have been simulated to obtain and analyze temperature, pressure, and velocity fields of flow. The results show that geometrical parameters of the plates such as Chevron angle have indisputable effects on flow pattern and heat transfer of the heat exchanger. Finally, the effects of Chevron angle and Reynolds number (4000£Re£20000) on friction factor and Nusselt number of the flow were studied and compared with available experimental results. The numerical results show a good agreement with the experimental data.

Experimental investigations have been done to find out the heat transfer characteristics and friction factor of water based Al2O3 nanofluids as a coolant in brazed plate heat exchangers. In most of the studies plate heat exchangers are used in horizontal or vertical conditions. The base plate of the plate heat exchanger was kept inclined at (0o, 30o, 60o, 90o). The experimentation has been carried out with two different concentration of the nanofluids (0. 1 v/v% and 0. 2 v/v%). It was observed that the heat transfer characteristics improves with an increase in Reynolds number. It has been shown that nanofluids in a plate heat exchanger have a maximum of 34% heat transfer rate over the base fluid. It has been observed that from horizontal to vertical orientation heat transfer rate decreases with increase in Reynolds number. The average heat transfer coefficient has been found to reduce by 10-15% when the angle of inclination of base plate of heat exchanger i from horizontal is 30o.

This paper describes the problem of channel blockage as a result of flow maldistribution between the channels of a model mini channel plate heat exchanger consisting of one pass on each leg. Each leg of the heat exchanger contains 51 parallel and rectangular minichannels of four hydraulic diameters namely 461 μ m, 571 μ m, 750 μ m and 823 μ m. In addition, a more complex geometry has been investigated where for the sake of breaking the development length the inclined transverse cuts have been incorporated. The moment of liquid phase transition through the exchanger (the working medium: water) was recorded for the mass fluxes ranging from 18. 67 to 277. 76 kg/m2s in 51 parallel channels with the use of a fast speed camera. The Reynolds numbers Re in the individual channels were from 10. 76 to 90. 04. The relationship between the mass flux and the size of the minichannels in the presence of the maldistribution is discussed here. The existence of the threshold in the mass flux below which the phenomenon occurs has been shown. Two mechanisms of channel blocking have been recorded and described in detail. A miniscale variation of one of them containing the extended geometry was created as well.

Unsteady three-dimensional DNS and LES simulations for resolutions up to about 1.2 million points were performed to investigate the fluid flow and heat transfer in a plate-fin heat exchanger with vortex generators. The Prandtl and Reynolds numbers are 0.71 and 2000, respectively. An incompressible finite volume code based on a fractional step technique with a nonstaggered grid arrangement and a multigrid pressure Poisson solver was used. From these simulations, the heat transfer and fluid flow were studied using instantaneous and time-averaged quantities such as the velocity components, pressure, vorticity, turbulent stresses, temperature fluctuations and Nusselt number. This study shows that the temperature fluctuations, the turbulent kinetic energy, and the unsteadiness effects are stronger in the regions, where the longitudinal vortices are more active. In this study, the effects of spatial resolution and the angle of incidence of the vortex generators are also investigated. A comparison between DNS and LES simulations for the present study shows that the predicted structures of fluid flow and temperature fields are similar for both methods

heat exchangers are widely used in power engineering and industrial applications. Many techniques such as coiled tube, surface tension devices, rough surfaces and extended surfaces have been investigated to enhancethermal performance and minimize the cost and size of the heat exchanger equipment. One of the most important techniques is tube insert. In general, tube inserts can be classified into two broad categories: stationary inserts and self-rotating inserts. Compared with stationary inserts, the self-rotating inserts can rotate in the tube by fluid and the comprehensive performance of self-rotating inserts is improved significantly. This paper mainly focuses on reviewing the large number of experimental and numerical works taken by researchers on self-rotating inserts such as twisted tapes, miniature hydraulic turbine, turbine-type swirl generators, etc. To improve the thermal efficiency of heat exchanger and serviceable to designers implemention of passive enhancement techniques in heat exchanger are required. The authors found that self-rotating inserts can streng then the heat transfer efficiency, meanwhile achieve on-line automatic anti-scaling and descaling effect. When the fluid velocity is more than 0.2m/s, most of self-rotating inserts can be applied. The heat transfer performance and frictional loss have been discussed to get the optimal configuration of self-rotating inserts. The convective heat transfer correlations have also been discussed. Determining how to find the optimal self-rotating insert is the main objective of this paper.

Optimum design of heat exchanger networks is an important subject in process design practice. Scientists and researchers have put a lot of effort to develop new methodologies for design and optimization of such networks, using both mathematical and conceptual approaches. In conventional pinch analysis, as a conceptual approach, an initial network is first synthesized using pinch design method, and then optimized by implementation of appropriate rules and techniques. However, these rules and techniques do not involve pressure drop considerations. In a recent research, new optimization methodology has been developed that includes three stages, each of which comprises many algorithms. The first stage of this methodology, which focuses on heat load optimization, is explained in this article. The method of heat load optimization in this paper is based on this loop breaking rules and techniques, and at the same time makes use of mathematical programming to find optimum point. Due to the differences between the nature of grass-root and retrofit projects, different procedures have been developed accordingly. These new procedures have also been applied to two case studies (Aromatics as grass-root, and crude distillation unit, as retrofit) and the results proved to be as expected.Having optimized the two initial networks, 4 percent improvement in total annual cost of aromatics network and 6.5 percent improvement in investment or 11 percent improvement in payback of the CDU network were identified.