convective heating
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Author(s):  
Tetiana Rymar

Heating the air in the boiler air heater with the heat of fuel combustion products performs the functions of increasing the fuel combustion temperature, increasing the temperature level of gases in convective heating surfaces, improving ignition and fuel combustion conditions, increasing boiler efficiency by utilizing waste gas heat, improving fuel quality due to its preliminary supply, etc. However, the peculiarities of the process of heating the air in the air heaters do not allow to achieve a decrease in the temperature of the exhaust gases. This is due to the unfavorable ratio of heat capacities of flue gases and air, as well as corrosion and contamination of the heating surfaces of air heaters. The research of heat transfer processes and hydraulic resistance of unified package of cold layer of RAH is depicted at this work. The graphic dependence of the change in the coefficient of hydraulic resistance and Nu number for unified packages with single line of sheets and simplified profile with corrosion resistance enamel from the Reynolds number for different values of the length of the replaced areas was constructed. The unified packing of the simplified profile has increased by 1.17 times equivalent diameter and is characterized by good operational parameters and takes into account the risk of contamination of heating surfaces due to the enamel coating.


2021 ◽  
pp. 1-39

Abstract The radiative cooling rate in the tropical upper troposphere is expected to increase as climate warms. Since the tropics are approximately in radiative-convective equilibrium (RCE), this implies an increase in the convective heating rate, which is the sum of the latent heating rate and the eddy heat flux convergence. We examine the impact of these changes on the vertical profile of cloud ice amount in cloud-resolving simulations of RCE. Three simulations are conducted: a control run, a warming run, and an experimental run in which there is no warming but a temperature forcing is imposed to mimic the warming-induced increase in radiative cooling. Surface warming causes a reduction in cloud fraction at all upper tropospheric temperature levels but an increase in the ice mixing ratio within deep convective cores. The experimental run has more cloud ice than the warming run at fixed temperature despite the fact that their latent heating rates are equal, which suggests that the efficiency of latent heating by cloud ice increases with warming. An analytic expression relating the ice-related latent heating rate to a number of other factors is derived and used to understand the model results. This reveals that the increase in latent heating efficiency is driven mostly by 1) the migration of isotherms to lower pressure and 2) a slight warming of the top of the convective layer. These physically robust changes act to reduce the residence time of ice along at any particular temperature level, which tempers the response of the mean cloud ice profile to warming.


Abstract The sporadic formation of short-lived convective clouds in the eye of Tropical Cyclone (TC) Trami (2018) is investigated using dropsonde data and simulation results from a coupled atmosphere–ocean model. According to the satellite data, top height of the convective clouds exceeds 9 km above mean sea level, considerably taller than that of typical hub clouds (2–3 km). These clouds are located 10–30 km away from the TC center. Hence, these convective clouds are called deep eye clouds (DECs) in this study. The dropsonde data reveal increase in relative humidity in the eye region during the formation of DECs. Short-lived convective clouds are simulated up to the middle troposphere in the eye region in the coupled model. Investigation of thermodynamic conditions shows a weakened low-level warm core and associated favorable conditions for convection in the eye region during the formation of DECs. DECs are formed after the weakening and outward displacement of convective heating within the eyewall. To elucidate the influence of the changes in convective heating within the eyewall on the formation of DECs, we calculate secondary circulation and associated adiabatic warming induced by convective heating within the eyewall using the Sawyer–Eliassen equation. In the eye region, weakenings of subsidence and associated vertical potential temperature advection are observed as DECs are formed. This suggests that the weakening and outward displacement of convective heating within the eyewall create favorable conditions for the sporadic formation of DECs.


MAUSAM ◽  
2021 ◽  
Vol 48 (2) ◽  
pp. 135-156
Author(s):  
MUKUT B. MATHUR

ABSTRACT. Condensational heating is a primary source of energy for disturbances like a tropical storm. The resolvable scale condensation and the parameterized convection, in many fine mesh numerical models, are evaluated at intervals greater than the time step, order of a minute, used for computing dynamical processes. The latent heating may depend on the model resolution and the interval at which the precipitation physics is evaluated. Numerical results from a series of short range forecasts are compared to study the impact of varying the horizontal resolution and the interval for evaluating condensation physics, and of excluding the parameterized convective heating. A horizontal grid spacing of 40 km (coarse mesh) or 20 km (fine mesh) in National Centers for Environmental Prediction's Quasi-Lagrangian Model (QLM), and the initial data for a tropical storm case, are utilized. Resolvable scale condensation is invoked only at supersaturated grid points, and a Kuo-type convective parameterization procedure is employed.   Significant structural differences are produced when the interval for computing both parameterized convection and resolvable scale heating is changed, and these differences broaden when the horizontal resolution is increased. The central warm cote structure and storm intensity are simulated better when both condensational processes are evaluated at an interval of twelve time steps than at each time step. Vertical columns in central storm area rapidly become convectively stable, and the maximum in vertical motion and strongest horizontal winds shift in the outer storm area, when both condensational processes are invoked at each time step. The central storm area remains conditionally unstable, and strongest winds develop close to the center, when both condensational processes are evaluated at intervals of twelve time steps.   The central storm area remains conditionally unstable also in the fine mesh experiment in which the parameterized convective heating is excluded and the resolvable scale heating is evaluated at each time step. Intense vertical motion and vigorous heating develop in deep vertical columns, indicating that the heating on the convective scale is simulated as the resolvable scale heating. The vertical distribution of heating and the storm structure, during the first six hours in this case, are similar to those in the fine mesh run in which both condensational processes are evaluated at intervals of twelve time steps. However, the storm intensifies more rapidly after 6 h in the former than in the later case. Numerical results from additional experiments are presented to show that predicted storm structure is modified with a change in interval for invoking either or both condensational processes, and these circulation differences are not due to the initial spin up.   Transfer of moisture and heat from low levels into the higher troposphere in cumulonimbus clouds takes place in several minutes. Above cited and other predictions from the QLM suggest that storm structure. intensity and motion in a mesoscale model are likely to, be improved when parameterized convective heating is included; however, a parameterization scheme that concurrently produces alterations in the entire model cloud depth should be invoked at intervals of several minutes.      


Author(s):  
P. I. Shustov ◽  
A. S. Lukin ◽  
X.‐J. Zhang ◽  
A. V. Artemyev ◽  
A. A. Petrukovich ◽  
...  

Materials ◽  
2021 ◽  
Vol 14 (23) ◽  
pp. 7443
Author(s):  
Cezary Senderowski ◽  
Andrzej J. Panas ◽  
Bartosz Fikus ◽  
Dariusz Zasada ◽  
Mateusz Kopec ◽  
...  

In this paper, dynamic interactions between the FeAl particles and the gaseous detonation stream during supersonic D-gun spraying (DGS) conditions into the water are discussed in detail. Analytical and numerical models for the prediction of momentum and complex heat exchange, that includes radiative effects of heat transfer between the FeAl particle and the D-gun barrel wall and phase transformations due to melting and evaporation of the FeAl phase, are analyzed. Phase transformations identified during the DGS process impose the limit of FeAl grain size, which is required to maintain a solid state of aggregation during a collision with the substrate material. The identification of the characteristic time values for particle acceleration in the supersonic gas detonation flux, their convective heating and heat diffusion enable to assess the aggregation state of FeAl particles sprayed into water under certain DGS conditions.


Vestnik MGSU ◽  
2021 ◽  
pp. 1599-1607
Author(s):  
Mikhail V. Bodrov ◽  
Aleksandr A. Smykov

Introduction. It has been repeatedly proven that the use of radiant heating systems leads to an increase in the environmental safety of industrial premises by increasing their energy efficiency. The most promising solution is the use of gas infrared emitters, in which there is no intermediate coolant, and the heat of combustion of the gas enters the room. However, such a solution has a number of limitations on gas availability, comfort and fire hazard. Also, a highly efficient solution is the use of water infrared emitters, which can be represented by emitting panels or emitting profiles that use an intermediate coolant, but do not have many limitations inherent in gas systems. Materials and methods. This study was conducted in the Laboratory of radiant Heating of NNGASU and is devoted to the study of the peculiarities of the formation of the temperature regime in rooms heated by water infrared radiators, as well as the thermal regime of external enclosing structures in these rooms. Results. Based on the results of the experiments, the authors concluded about the formed thermal regime in rooms with heating systems based on water infrared emitters. It is proved that the use of radiant heating leads to a more uniform temperature regime in a heated room, and less overheating of the room covering than when using convective heating systems. Conclusions. The energy efficiency of the use of radiant heating systems based on water infrared emitters has been proven. The study showed that the system of water radiant heating allows to reduce the gradient of air temperature in height not only in large-volume rooms, such as workshops, depots, gyms, but also in rooms with a low height of the coating location. This feature allows you to reduce heat losses through the coating. The temperature regime in the working area of the room with the use of radiant water heating, in comparison with convective, remains unchanged.


2021 ◽  
Author(s):  
Shuheng Lin ◽  
Song Yang ◽  
Shan He ◽  
Zhenning Li ◽  
Jiaxin Chen ◽  
...  

AbstractAtmospheric diabatic heating, a major driving force of atmospheric circulation over the tropics, is strongly confined to the tropical western North Pacific (TWNP) region, with the global warmest sea surface temperature (SST). The changes in diabatic heating over the TWNP, which exert great impacts on the global climate system, have recently exhibited a noticeable seasonal dependence with a remarkable increase in boreal spring. In this study, we applied observations, reanalysis data, and numerical experiments to investigate the causes of the seasonality in heating changes. Results show that in boreal spring convection is more sensitive to the TWNP SST, leading to a more significant enhancement of deep convection, although the increase in the SST is nearly the same as that in the other seasons. In the non-spring seasons, the enhanced convection due to increased local SST is suppressed by the anomalous anticyclonic wind shear over the TWNP, generated by the easterly wind anomalies induced by the tropical Indian Ocean (TIO) warming via the Kevin waves. However, the TIO warming does not show any suppressing effect in spring because it is much weaker than that in the other seasons and thus the warming itself cannot induce sufficient convective heating anomalies to excite the Kelvin waves.


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