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Heat Recovery
Published in Neil Petchers, Combined Heating, Cooling & Power Handbook: Technologies & Applications, 2020
Fouling factors must be considered in all heat exchanger selections. Fouling reduces the efficiency of heat transfer because it reduces the overall heat transfer coefficient. Usual causes include: external tube deposits, such as oil films or solids from a liquid or gaseous stream; internal tube-surface scaling due to precipitation of solid compounds from solution; or corrosion of surfaces, external or internal. To minimize fouling, natural gas exhaust is preferred. Using gas rather than oil will allow greater heat transfer efficiency and smaller heat exchange surface requirements.
Energy use in industry, analysis and management of energy use
Published in Kornelis Blok, Evert Nieuwlaar, Introduction to Energy Analysis, 2020
Kornelis Blok, Evert Nieuwlaar
Table 4.1 shows some typical values for the heat transfer coefficient k. From these numbers, we see that heat exchange between two liquid flows requires much less heat exchange surface area than between two gas flows. The heat transfer coefficient depends on the physical properties of the fluid media, the surface characteristics of the heat exchanging area, the fluid velocities, etc.
Modelling of Heat Transfer During Deep Fat Frying of Food
Published in Surajbhan Sevda, Anoop Singh, Mathematical and Statistical Applications in Food Engineering, 2020
KK Dash, Maanas Sharma, MA Bareen
The heat transfer coefficient is a critical processing parameter that plays a vital role in frying. The heat transfer coefficient is a measure of how fast heat transfer occurs between a surface and a fluid. For transient heat transfer analysis, the concepts of the Reynolds number (Re), Prandtl number (Pr), Grashof number (Gr), and Nusselt number (Nu), which are dimensionless terms used to determine the overall convection heat transfer coefficient, h, need to be introduced.
Performance optimization of multiple stage evaporator using interior-point method and metaheuristic approaches in environment of real-time plant complexities
Published in International Journal of Green Energy, 2021
Smitarani Pati, Om Prakash Verma
Moreover, almost all the above-discussed energy models have been analyzed under the assumption of ideal conditions (such as heat loss, Boiling Point Elevation (BPE), and Fouling & Scaling effect) present in the real-time plant environment. However, few literature addresses these issues, such as the effect of BPE on the temperature (Ferreira et al. 2011) and hence, on SE. BPE depends on the concentration of the black liquor and causes enhancement in vapor temperature, which is directly related to the SC. It has been qualitatively demonstrated that with an increase in BPE, there is a decrease in the SE of the MSE (R. Bhargava et al. 2008aa; R., 2008). Further, the effect of fouling is, of course, also an essential part of the Kraft recovery process and described through experimental studies done in previous literature (Abd-Elhady, Malayeri, and Müller-Steinhagen 2011; Gourdon 2000; Müller-Steinhagen and Branch 1997). Fouling occurs due to inorganic water-soluble sodium salts (Na2SO4 and Na2CO3) in the black liquor. With the increase in fouling effect, there is an enhancement in temperature difference and hence, a decrease in overall heat transfer coefficient, which leads to a reduction in energy efficiency. The fouling depends on various parameters such as flow velocity, temperature difference, mass flow rate, etc., and their interdependency can be correlated to study the effect of fouling on the MSE (Gautami and Khanam 2012). The present work addresses the various issues raised in the above discussions, and it may be sketched as follows:
A comprehensive review on the heat transfer and nanofluid flow characteristics in different shaped channels
Published in International Journal of Ambient Energy, 2021
Heat transfer can be increased by giving different approaches and techniques, such as raising either the heat transfer surface or the heat transfer coefficient between the fluid and the surface that allow significant heat transfer rates in a short volume. Many engineering applications are within the scientific areas such as cooling system for micro-electronic devices, heat exchangers, solar collectors, underground cable systems and so forth. Challenge of engineers and scientists is to develop a generalisation of basic formulation for heat transfer from wavy surfaces, channels, tubes and cavities having wavy walls in presence or absence of porous media and nanoparticles (Shenoy, Sheremet, and Pop 2016). Cooling is one of the most remarkable technical challenges dealing with many diverse industries, consisting of microelectronics, transport, solid-state lighting, and manufacturing (Manca, Jaluria, and Dimos 2010). The focus on the area of flow and heat transfer past wavy surfaces in complex enclosures like square, trapezoidal, and rectangular using nanofluids has been intensifying over the years due to the increasing interest of researchers from applied mathematics, mechanical, and chemical engineering as well as from biomechanics and engineering mechanics (Sheremet and Pop 2017).
Heat transfer and pressure drop performance of alumina–water nanofluid in a flat vertical tube of a radiator
Published in Chemical Engineering Communications, 2018
Gurpreet Singh Sokhal, Dasaroju Gangacharyulu, Vijaya Kumar Bulasara
The effects of fluid inlet temperature, air velocity, Reynolds number, and particle concentration on thermal and flow behavior of nanofluids in a vertical flat tube of a radiator were investigated. The thermal conductivity enhanced significantly (>20%) with an increase in particle concentration and temperature. The density and viscosity increased with an increase in the particle concentration, while they both decreased with an increase in temperature. The deviation between viscosity of nanofluids and base fluid reduced with an increase in temperature. The heat transfer rate increased with an increase in fluid inlet temperature, particle concentration, Reynolds number as well as air inlet velocity. The maximum enhancement in heat transfer coefficient was about 31% at 1.0% (v/v) concentration as compared to the base fluid. This enhancement was more than the enhancement in the thermal conductivity of nanofluid at same temperature and concentration. This indicates that besides thermal conductivity, other factors such as fluid inlet temperature, Reynolds number, and air velocity also affect heat transfer coefficient. The pressure drop increased with an increase in the Reynolds number and particle volume concentration, while it slightly decreased with an increase in fluid inlet temperature because density and viscosity decrease with an increase in temperature. The maximum pressure drop observed for 1.0 vol.% nanofluids was 1.88 times that of the base fluid at the highest Reynolds number (≈30,000). Friction factor and pumping power also increased with particle concentration because both depend on the pressure drop. The friction factor decreased while pumping power increased with an increase in Reynolds number. However, in case of radiators, heat transfer is the primary concern (than pressure drop). This study proved that the use of nanofluids in place of base fluid increases the heat transfer rate, which leads to reduction in size of automotive radiator.