Industrial high-temperature processes require heat exchangers that remain thermally effective while satisfying hydraulic and geometric constraints across strongly temperature-dependent refrigerant states. This study develops a modular, segment-by-segment coupled thermal-hydraulic framework for the preliminary design of hydrocarbon heat exchangers from prescribed process boundary conditions. Local thermophysical properties, phase regime, heat transfer coefficients, pressure losses, temperature profiles, required area, geometry screening, and feasibility assessment are solved consistently. Concentric-tube and preliminary TEMA-E shell-and-tube configurations are evaluated for brewery water heating and spray-dryer air heating using n-butane, isobutane, n-pentane, and isopentane. In the fixed-terminal-temperature brewery n-butane study, the minimum heat-exchanger area occurred at 42.52 bar, or 1.12 times the critical pressure; this represents an exchanger-level pressure selection rather than a system-level optimum. The corresponding concentric and shell-and-tube designs required 16.45 and 20.98 m², respectively. No feasible smooth-tube spray-dryer design was obtained within the investigated domain because low air-side heat transfer combined with excessive length, velocity, pressure drop, or shell-count requirements. Correlation sensitivity was below 1
This study establishes a segmented non-dimensional thermal correlation ( Nu_p=A ∙ Re_p^m ∙ Pr^n ) for gas-solid fluidized beds during the critical thermochemical conversion a semi-pilot batch of Ammonium Uranyl Carbonate (AUC) into high-density Uranium Dioxide (UO2) nuclear fuel precursors. Operating inside a fluidized bed reactor across an active volumetric flow rate spectrum from 0 to 90 L/min (0 ≤ Vg ≤ 0.183 m/s), local convective heat transfer coefficients (h) were examined against multi-point bed pressure drop (ΔP) values up to a reduction isotherm of 600 °C. The structural originality of this work relies on decoupling the dual physical mechanisms of powder agglomeration along the reaction pathway. For the low-temperature drying domain (T ≤ 200 °C), ordinary least-squares graphical linearizations extract a highly convective multi-particle closure governed by Nu_p=0.58 ∙ Re_p^0.68 ∙ Pr^1/3 . Within this zone, moisture-bound macro-clusters experience intense, beneficial hydro-mechanical aggregate shear fracture and cluster erosion, driving the local transport capacity to a maximum experimental value of hexp = 107.40 W/m2∙K, corresponding to the analytical prediction htheo = 106.91 W/m2∙K. Conversely, advancing across the 600 °C advanced hydrogen reduction limit generates a 46 mbar bed pressure drop collapse (from 91.0 mbar down to 45.0 mbar), providing direct empirical evidence of solid-state crystalline sintering densification ( ρ _s ∼ 10. 960 g/cm3). The stagnant granular agglomeration appears to create a local thermal barrier that may condense the insulating film of stagnant gas, which is consistent with the high-temperature correlation obtained Nu_p=0.28 ∙ Re_p^0.38 ∙ Pr^1/3 . This visco-inertial phenomenon limits the effective transport performance to an apparent ceiling, where where hexp = 38.36 W/m²∙K and htheo = 38.73 W/m²∙K).
Solar air heaters (SAHs) are widely utilized in thermal applications, but their overall efficiency is often constrained by low air-side heat transfer coefficients. This study presents a novel approach to enhance collector performance by integrating a spray-deposited MXene nanocoating onto a V-corrugated absorber plate. Experimental evaluations were conducted across a Reynolds number range of 2200 to 11,000 under controlled solar radiation conditions. Performance metrics were benchmarked against conventional flat plate and V-corrugated absorbers under identical operating parameters. The results demonstrate that the MXene-coated V-corrugated absorber significantly enhances surface thermal transport, yielding Nusselt number ratios (Nu/Nu0) of 1.85 to 2.42 while maintaining moderate friction factor ratios (f/f0) of 1.45 to 1.82. Consequently, maximum thermal efficiency improved from 52
Despite the solar chimney’s merits in reducing fossil fuel consumption, it often requires design enhancements to meet the ventilation demands of buildings. In this vein, varying techniques have been utilized to boost their heat transfer performance. In the present study, the thermo-hydraulic performance of double-channel solar chimneys versus different absorber-glazing distances is numerically investigated under different inclination angles, evaluating their potential for compact architectural integration. The solar radiation is modeled using the solar ray-tracing method in ANSYS Fluent, enabling the calculation of the incident solar radiation on the solar chimney. The investigated chimney geometry had a height of 150 cm, a width of 62 cm, and a channel gap of 40 cm. The chimney inclination angle was varied from 0° to 45°. For the double-channel configuration, the absorber plate was positioned at distances of 10, 15, 20, 25, and 30 cm from the glass cover to evaluate its effect on ventilation performance. Unlike prior studies that focus on single-channel systems, this work provides a comparative investigation into the geometric optimization of double-channel configurations, assessing the synergy between absorber plate positioning and inclination angles. The CFD study is performed under the ambient conditions of Tehran, Iran. The numerical results demonstrate that the double-channel configuration achieves an 18.5
It has been experimentally demonstrated that the diffusion of Ru atoms into PbO–SiO2 glass during firing directly determines the electrical conductivity σ and thermo-EMF generation (Seebeck effect) in thick-film resistors. Investigations of the distributions of the ruthenium atoms concentration (using energy-dispersive spectroscopy), spreading resistance, and the Seebeck coefficient in the diffusion layer on beveled samples have established a correlation between these parameters. The spatial distribution of of these parameters is described by the complementary error function (erfc), indicating a constant diffusion coefficient within the investigated range. Near the “diffusion layer–glass” interface, the Seebeck coefficient S reaches 5–7 mV/K, whereas at the “glass–RuO2” interface, it is on the order of a few µV/K. The diffusion length estimated from the measurements exceeds 100 μm which is significantly greater than the average distance between RuO2 particles (less than 1–2 μm); this confirms that under standard processing conditions (10 min at 850 °C), the glass matrix of thick-film resistors undergoes uniform doping and acquires high electrical conductivity.
