This paper presents single-phase shell side heat transfer performance of a vertically oriented shell and tube bundle. Steady-state single-phase experiments were conducted to determine the shell side Nusselt number with water and water/glycol solution as working fluids for both counter and parallel flow configurations. Experiments were carried out for Reynolds number varying from 3000 to 15,000 with Prandtl number ranging from 10 to 20. Counter flow configuration showed slightly better performance. Nusselt number correlations are presented for both configurations using a modified Wilson plot method. Comparison of results with previous studies and commercial software are presented. Thermal performance for all flow rate conditions showed close comparison to the results from a reputable commercial software. The correlation was further validated by comparing results for 30 different cases to calculations from 2 widely used commercial softwares. Comparison showed that the correlation can be used for the design of single-phase single segmental shell and tube heat exchangers.

The shell condenser is one of the key components of underwater vehicles. To study its thermal performance and to design a more efficient structure, a computational model is generated to simulate condensation inside straight and helical channels. The model combines empirical correlations and a MATLAB-based iterative algorithm. The vapor quality is used as a sign of the degree of condensation. Three calculation models are compared, and the optimal model is verified by a comparison of simulated results and available experimental data. Several cases are designed to reveal the effects of various inlet conditions and the diameter-over-radius (D h / R) ratio. The results show that the inlet temperature and mass rate significantly affect the flow and heat transfer in the condensation process, the heat transfer capabilities of the helical channels are much better than that of the straight channel, and both the heat transfer coefficient and total pressure drop increase with the decrease of D h / R . This study may provide a useful reference for performance prediction and structural design of shell condensers used for underwater vehicles and may provide a relatively universal prediction model for condensation in channels.

This paper explores the use of a self-adaptive multipopulation elitist (SAMPE) Jaya algorithm for the economic optimization of shell-and-tube heat exchanger (STHE) design. Three different optimization problems of STHE are considered in this work. The same problems were earlier attempted by other researchers using genetic algorithm (GA), particle swarm optimization (PSO) algorithm, biogeography-based optimization (BBO), imperialist competitive algorithm (ICA), artificial bee colony (ABC), cuckoo-search algorithm (CSA), intelligence-tuned harmony search (ITHS), and cohort intelligence (CI) algorithm. The Jaya algorithm is a newly developed algorithm and it does not have any algorithmic-specific parameters to be tuned except the common control parameters of number of iterations and population size. The search mechanism of the Jaya algorithm is upgraded in this paper by using the multipopulation search scheme with the elitism. The SAMPE-Jaya algorithm is proposed in this paper to optimize the setup cost and operational cost of STHEs simultaneously. The performance of the proposed SAPME-Jaya algorithm is tested on four well-known constrained, ten unconstrained standard benchmark problems, and three STHE design optimization problems. The results of computational experiments proved the superiority of the proposed method over the latest reported methods used for the optimization of the same problems.

A 3D computational fluid dynamics (CFD) modeling study has been carried out for the tin bronze (C903) slab of industrial size in a vertical direct chill caster. The melt is delivered from the top across the entire cross section of the caster. An insulated hot-top is considered above the 80-mm mold to control the melt level in the mold. A porous filter is considered in the hot-top region of the mold to arrest the incoming inclusions and homogenize the flow into the mold. The melt flow through the porous filter is modeled on the basis of the Brinkmann–Forchheimer-extended non-Darcy model. Results are obtained for four casting speeds varying from 40 to 100 mm/min. The metal–mold contact region, as well as the convective heat transfer coefficient at the mold wall, is also varied. In addition to the above, the Darcy number for the porous media is also changed. All parametric studies are performed for a fixed inlet melt superheat of 62 °C. The results are presented pictorially in the form of temperature and velocity fields. The sump depth, mushy region thickness, solid shell thickness (ST) at the exit of the mold, and axial temperature profiles are also presented and correlated with the casting speed through regression analysis.

A methodology has been developed for coupling the one-dimensional (1D) solution of flow inside the nonpermeable channels with the 3D outer flow in shell and tube type of configurations. In the proposed reacting channel, the 1D channels have detailed reactions while the outer 3D flow can be reactive or nonreactive. The channels are discretized into 1D grid points and a parabolic solver is used to solve the species transport and energy equations inside the channels. Since the walls of the channels are nonpermeable, the two zones are coupled only through the heat transfer. The current approach is tested and validated for a series of problems with increasing complexities. The predictions of the channel model (CM) are compared with 3D modeling of the channels and experimental data. The CM predictions are in excellent agreement with the fully resolved (FR) model with much less computational cost. The discussed methodology is useful for applications such as fuel reformers, hydrocarbon cracking furnaces, heat exchangers, etc.

Shell and tube heat exchanger (STHX) is a class of indirect contact heat exchangers which has wide applications in various industries. In this paper, the shell-side performance characteristics of a small STHX with differently notched continuous helical baffle (CHB) geometries are numerically studied and compared with same CHB without notched regions. The indentations are uniquely produced by placing the notch near the core of the heat exchanger, thereby conferring the flow with low-pressure drop regions. Two set of models of inner notched continuous helical baffle (ICHB), i.e., ICHB1 and ICHB2, are studied with notch width of about 5% and 10% of the inner shell diameter of the same heat exchanger. In comparison with the CHBSTHX, it is seen that the STHXs incorporated with ICHBs, the heat transfer rate dropped slightly, but a significant decrease in pressure drop is observed. It is found that the heat transfer coefficient to pressure drop ratio for ICBH1 and ICHB2 shows significant increase in comprehensive performance of about 3.5% and 32.42%, respectively, when compared with same CHB without notched regions.

A methodology is developed for the design of an air-cooled 55-kW-rated inverter heat sink. The design constraints are that the power density (PD) must meet or exceed the values associated with liquid-cooled systems of the same power rating, and that the maximum surface temperatures be less than 200 °C. To keep the pressure drop low relative to turbulent flow designs, a laminar flow regime is chosen. A preliminary design that satisfies the PD constraint exactly, and the thermal requirements approximately, is determined. To ensure that the thermal requirements are met by the design configuration, a thermal-fluid analysis based on a three-dimensional conjugate heat transfer model is conducted. Overall, energy balance errors (OEBEs) as high as 15% were encountered in the numerical models. These errors are reduced by taking advantage of the symmetry between fins using a typical unit cell model. A new simplified approach for the simulations was identified which involved modeling fins as highly conductive layers instead of solid domains. This further reduced the OEBEs to less than 0.004%. The design factors considered in this study include effective cooling surface area, fin thickness, fin spacing, and fin height. The results show that the maximum surface temperatures can be kept below 200 °C for safe operation of SiC devices in the inverter module while increasing the PD.

The present work introduces an experimental study of horizontal shell and coil heat exchangers. Characteristics of the convective heat transfer in this type of heat exchangers and the friction factor for fully developed flow through their helically coiled tube (HCT) were investigated. The majority of previous studies were performed on HCTs with isothermal and isoflux boundary conditions or shell and coil heat exchangers with small ranges of HCT configurations and fluid-operating conditions. Here, five heat exchangers of counterflow configuration were constructed with different HCT torsions ( λ ) and tested at different mass flow rates and inlet temperatures of both sides of the heat exchangers. In total, 295 test runs were performed from which the HCT-side and shell-side heat transfer coefficients were calculated. Results showed that the average Nusselt numbers of both sides of the heat exchangers and the overall heat transfer coefficient increase by decreasing coil torsion. At lower and higher HCT-side Reynolds number ( Re t ), the average increase in the HCT-side average Nusselt number ( Nu ¯ t ) is of 108.7% and 58.6%, respectively, when λ decreases from 0.1348 to 0.0442. While, at lower and higher shell-side Reynolds number ( Re sh ), the average increase in the shell-side average Nusselt number ( Nu ¯ sh ) is of 173.9% and 69.5%, respectively, when λ decreases from 0.1348 to 0.0442. In addition, a slight increase of 6.4% is obtained in the HCT Fanning friction factor ( f c ) at lower Re t when λ decreases from 0.1348 to 0.0442, and this effect vanishes with increasing Re t . Furthermore, correlations for Nu ¯ t , Nu ¯ sh , and f c are obtained.

Phase change thermotropic materials have been proposed as a low cost method to provide passive overheat protection for polymer solar thermal absorbers. One challenge to their development is control of the size of the phase change particles dispersed within the matrix. Here we explore encapsulation as a means to resolve this challenge with a focus on the selection of materials, including the encapsulating shell, to achieve desirable optical behavior. Hydroxystearic acid (HSA) particles in a matrix of poly(methyl methacrylate) (PMMA) is down selected from candidate materials based on its optical properties and the melt temperature of the dispersed phase. The optical properties (normal-hemispherical transmittance, reflectance, and absorptance) as a function of the properties of the encapsulation shell and the particle volume fraction are predicted at a wavelength of 589 nm using a Monte Carlo ray tracing model. A range of shell relative refractive indices, from 0.95 to 1, and thicknesses, up to 35 nm, can be employed to achieve greater than 80% transmittance in the clear state and greater than 50% reflectance in the translucent state.

This study presents an experimental investigation of the characteristics of convective heat transfer in horizontal shell and coil heat exchangers in addition to the friction factor for fully developed flow through their helically coiled tube (HCT). Five heat exchangers of counterflow configuration were constructed with different HCT-curvature ratios ( δ ) and tested at different mass flow rates and inlet temperatures of γ -Al 2 O 3 /water nanofluid in the HCT. The tests were performed for γ -Al 2 O 3 with average size of 40 nm and particles volume concentration ( ϕ ) from 0% to 2% for 0.0392 ≤ δ ≤ 0.1194 . Totally, 750 test runs were performed from which the HCT-average Nusselt number ( Nu ¯ t ) and fanning friction factor ( f c ) were calculated. Results illustrated that Nu ¯ t and f c of nanofluids are higher than those of the pure water at same flow condition, and this increase goes up with the increase in ϕ . When ϕ increases from 0% to 2%, the average increase in Nu ¯ t is of 59.4–81% at lower and higher HCT-Reynolds number, respectively, and the average increase in f c is of 25.7% and 27.4% at lower and higher HCT-Reynolds number, respectively, when ϕ increases from 0% to 2% for δ = 0.1194 . In addition, results showed that Nu ¯ t and f c increase by increasing coil curvature ratio. When δ increases from 0.0392 to 0.1194 for ϕ = 2 % , the average increase in Nu ¯ t is of 130.2% and 87.2% at lower and higher HCT-Reynolds number, respectively, and a significant increase of 18.2–7.5% is obtained in the HCT-fanning friction factor at lower and higher HCT-Reynolds number, respectively. Correlations for Nu ¯ t and f c as a function of the investigated parameters are obtained.

A 3D numerical study is carried out for a vertical direct chill (DC) rolling ingot caster for an aluminum alloy (AA-5052). The model incorporated the coupled turbulent melt flow and solidification aspects of the casting process. The caster consists of a low-head hot-top mold. The melt is assumed to have been delivered through the entire top cross section of the caster. The previously verified in-house computational fluid dynamics (CFD) code is used to investigate the effects of the important parameters such as casting speed, inlet melt superheat, and mold-metal contact effective heat transfer coefficient (HTC) on the low-head casting process. It is found that the sump depth (SD), liquid depth, and mushy thickness (MT) at the center of the ingot increase linearly with the casting speed while the shell thickness (ST) at the exit of the mold decreases linearly with the casting speed. Useful correlations concerning the above quantities with casting speed have been provided for the benefit of DC casting operators.

In this paper, a numerical model of the molten salt furnace process was developed, by using computational fluid dynamics (CFD) technique and considering the gas flow, the combustion and the radiation heat transfer. The results demonstrate that the performances of the salt furnace could be improved by optimization using the numerical model. The temperatures along the circumference of the furnace coil and outside shell are quite even, and the deviant combustion phenomenon is not observed. A back-flow formed in the upper part of the furnace chamber enhances the circulation and the mixing of the gas and effectively stabilizes the combustion in the furnace. The behaviors of CO, CO2, NOx, and H2O are presented in terms of the gas flow, temperature distribution and volumetric concentration distribution. It is concluded that the furnace with the constant air flow rate of 15,500 Nm3/h and the guiding vane angle at 48–50 deg is optimized for the combustion effectiveness.

The present work experimentally investigates the characteristics of convective heat transfer in horizontal shell and coil heat exchangers in addition to friction factor for fully developed flow through the helically coiled tube (HCT). The majority of previous studies were performed on HCTs with isothermal and isoflux boundary conditions or shell and coil heat exchangers with small ranges of HCT configurations and fluid operating conditions. Here, five heat exchangers of counter-flow configuration were constructed with different HCT-curvature ratios (δ) and tested at different mass flow rates and inlet temperatures of the two sides of the heat exchangers. Totally, 295 test runs were performed from which the HCT-side and shell-side heat transfer coefficients were calculated. Results showed that the average Nusselt numbers of the two sides of the heat exchangers and the overall heat transfer coefficients increased by increasing coil curvature ratio. The average increase in the average Nusselt number is of 160.3–80.6% for the HCT side and of 224.3–92.6% for the shell side when δ increases from 0.0392 to 0.1194 within the investigated ranges of different parameters. Also, for the same flow rate in both heat exchanger sides, the effect of coil pitch and number of turns with the same coil torsion and tube length is remarkable on shell average Nusselt number while it is insignificant on HCT-average Nusselt number. In addition, a significant increase of 33.2–7.7% is obtained in the HCT-Fanning friction factor (fc) when δ increases from 0.0392 to 0.1194. Correlations for the average Nusselt numbers for both heat exchanger sides and the HCT Fanning friction factor as a function of the investigated parameters are obtained.

Global environmental and energy concerns have prompted the heating, ventilating, air-conditioning, and refrigeration industry to revisit the use of natural refrigerants. Nearly all natural refrigerants have superior transport properties as compared with synthetic refrigerants; however, the drawback with natural refrigerants has been their toxicity and flammability with an exception of carbon dioxide. In order to overcome this hurdle, it is essential that enhanced surface methods be developed and introduced to reduce the refrigerant charge in a system. Halocarbon industry has expended enormous amount of time and money in developing the ultrahigh efficiency heat exchangers. This experience and knowledge is available and could be applied in developing the efficient exchangers for natural refrigerant applications. This paper presents an overview of the status of natural refrigerants and the trends in the development of compact and low-charge systems.