Thermal Performance Analysis of Hydronic Ceiling Radiant Panel Heaters Under Different Parameters

2021 ◽  
pp. 1-40
Author(s):  
Tahir Dikmen ◽  
Tamer Calisir ◽  
Senol Baskaya
Keyword(s):  
Reynolds Number ◽  
Heat Load ◽  
Total Heat ◽  
Pipe Diameter ◽  
Heat Output ◽  
Inlet Temperature ◽  
Net Radiation ◽  
Heating Performance ◽  
Radiation Rate ◽  
Radiant Panel

Abstract A numerical analysis of a ceiling type radiant panel heater system was performed to examine the heating performance under different parameters, using the FloEFD code. Three-dimensional models of the room and radiant panel heater were created and the effects of the Reynolds number, water inlet temperature, pipe diameter and pipe runs on the heating performance of the system were examined in detail. The effects of these parameters on the total heat load, the net radiation rate, and the average surface temperature on the sheet and insulation material have been presented. The total heat load and net radiation rate obtained from the system increase with increase in the Reynolds number. Also, a rise in the water inlet temperature increases the heat output of the system. An increase of approximately 500 W was observed in the total heat output as the pipe diameter increased. It was observed, too, that the heat output increased with increase in pipe runs, although above a certain value the heat output became almost constant. The results of this study could offer information to engineers and manufacturers on the design and use of hydronic radiant systems.

A Method of Solving Three Temperature Problem of Turbine With Adiabatic Wall Temperature

2021 ◽  
Author(s):  
Zeyu Wu ◽  
Xiang Luo ◽  
Jianqin Zhu ◽  
Zhe Zhang ◽  
Jiahua Liu
Keyword(s):  
Heat Transfer ◽  
Numerical Simulation ◽  
Reynolds Number ◽  
Wall Temperature ◽  
Reference Temperature ◽  
Inlet Temperature ◽  
Adiabatic Wall ◽  
Rotating Cavity ◽  
Temperature Problem ◽  
Turbulence Parameters

Abstract The aeroengine turbine cavity with pre-swirl structure makes the turbine component obtain better cooling effect, but the complex design of inlet and outlet makes it difficult to determine the heat transfer reference temperature of turbine disk. For the pre-swirl structure with two air intakes, the driving temperature difference of heat transfer between disk and cooling air cannot be determined either in theory or in test, which is usually called three-temperature problem. In this paper, the three-temperature problem of a rotating cavity with two cross inlets are studied by means of experiment and numerical simulation. By substituting the adiabatic wall temperature for the inlet temperature and summarizing its variation law, the problem of selecting the reference temperature of the multi-inlet cavity can be solved. The results show that the distribution of the adiabatic wall temperature is divided into the high jet area and the low inflow area, which are mainly affected by the turbulence parameters λT, the rotating Reynolds number Reω, the high inlet temperature Tf,H* and the low radius inlet temperature Tf,L* of the inflow, while the partition position rd can be considered only related to the turbulence parameters λT and the rotating Reynolds number Reω of the inflow. In this paper, based on the analysis of the numerical simulation results, the calculation formulas of the partition position rd and the adiabatic wall temperature distribution are obtained. The results show that the method of experiment combined with adiabatic wall temperature zone simulation can effectively solve the three-temperature problem of rotating cavity.

scholarly journals Numerical Investigation on the Influence of Hot Streak Temperature Ratio in a High-Pressure Stage of Vaneless Counter-Rotating Turbine

2007 ◽  
Vol 2007 ◽  
pp. 1-14 ◽  
Author(s):  
Zhao Qingjun ◽  
Wang Huishe ◽  
Zhao Xiaolu ◽  
Xu Jianzhong
Keyword(s):  
High Pressure ◽  
Secondary Flow ◽  
Heat Load ◽  
Rotor Blades ◽  
Inlet Temperature ◽  
Combined Effects ◽  
Temperature Ratio ◽  
Flow Angle ◽  
Hot Streak ◽  
Relative Flow

The results of recent studies have shown that combustor exit temperature distortion can cause excessive heat load of high-pressure turbine (HPT) rotor blades. The heating of HPT rotor blades can lead to thermal fatigue and degrade turbine performance. In order to explore the influence of hot streak temperature ratio on the temperature distributions of HPT airfoil surface, three-dimensional multiblade row unsteady Navier-Stokes simulations have been performed in a vaneless counter-rotating turbine (VCRT). The hot streak temperature ratios from 1.0 (without hot streak) to 2.4 were used in these numerical simulations, including 1.0, 1.2, 1.6, 2.0, and 2.4 temperature ratios. The hot streak is circular in shape with a diameter equal to 25%of the span. The center of the hot streak is located at 50%of span and 0%of pitch (the leading edge of the HPT stator vane). The predicted results show that the hot streak is relatively unaffected as it migrates through the HPT stator. The hot streak mixes with the vane wake and convects towards the pressure surface (PS) of the HPT rotor when it moves over the vane surface of the HPT stator. The heat load of the HPT rotor increases with the increase of the hot streak temperature ratio. The existence of the inlet temperature distortion induces a thin layer of cooler air in the HPT rotor, which separates the PS of the HPT rotor from the hotter fluid. The numerical results also indicating the migration characteristics of the hot streak in the HPT rotor are predominated by the combined effects of secondary flow and buoyancy. The combined effects that induce the high-temperature fluid migrate towards the hub on the HPT rotor. The effect of the secondary flow on the hotter fluid increases as the hot streak temperature ratio is increased. The influence of buoyancy is directly proportional to the hot streak temperature ratio. The predicted results show that the increase of the hot streak temperature ratio trends to increase the relative Mach number at the HPT rotor outlet, and decrease the relative flow angle from 25%to 75%span at the HPT rotor outlet. In the other region of the HPT outlet, the relative flow angle increases when the hot streak temperature ratio is increased. The predicted results also indicate that the isentropic efficiency of the VCRT decreases with the increase of the hot streak temperature ratio.

scholarly journals Impact of Sediment Layer on Longitudinal Dispersion in Sewer Systems

Water ◽  
2021 ◽  
Vol 13 (22) ◽  
pp. 3168
Author(s):  
Marek Sokáč ◽  
Yvetta Velísková
Keyword(s):  
Reynolds Number ◽  
Layer Thickness ◽  
Dispersion Coefficient ◽  
Longitudinal Dispersion ◽  
Low Flow ◽  
Pipe Diameter ◽  
Sediment Layer ◽  
Pollution Transport ◽  
Sewer Pipes ◽  
Hydraulic Conditions

Experiments focused on pollution transport and dispersion phenomena in conditions of low flow (low water depth and velocities) in sewers with bed sediment and deposits are presented. Such conditions occur very often in sewer pipes during dry weather flows. Experiments were performed in laboratory conditions. To simulate real hydraulic conditions in sewer pipes, sand of fraction 0.6–1.2 mm was placed on the bottom of the pipe. In total, we performed 23 experiments with 4 different thicknesses of sand sediment layers. The first scenario is without sediment, the second is with sediment filling 3.4% of the pipe diameter (sediment layer thickness = 8.5 mm), the third scenario represents sediment filling 10% of the pipe diameter (sediment layer thickness = 25 mm) and sediment fills 14% of the pipe diameter (sediment layer thickness = 35 mm) in the last scenario. For each thickness of the sediment layer, a set of tracer experiments with different flow rates was performed. The discharge ranges were from (0.14–2.5)·10−3 m3·s−1, corresponding to the range of Reynolds number 500–18,000. Results show that in the hydraulic conditions of a circular sewer pipe with the occurrence of sediment and deposits, the value of the longitudinal dispersion coefficient Dx decreases almost linearly with decrease of the flow rate (also with Reynolds number) to a certain limit (inflexion point), which is individual for each particular sediment thickness. Below this limit the value of the dispersion coefficient starts to rise again, together with increasing asymmetricity of the concentration distribution in time, caused by transient (dead) storage zones.

scholarly journals Metabolic cost of feeding in Atlantic Cod (Gadus morhua) larvae using microcalorimetry

2006 ◽  
Vol 63 (2) ◽  
pp. 335-339 ◽  
Author(s):  
Artie McCollum ◽  
Jessica Geubtner ◽  
Ione Hunt von Herbing
Keyword(s):  
Gadus Morhua ◽  
Atlantic Cod ◽  
Metabolic Cost ◽  
Specific Dynamic Action ◽  
Total Heat ◽  
Heat Output ◽  
Larval Life ◽  
First Feeding ◽  
The Cost ◽  
Aerobic And Anaerobic

Abstract A microcalorimeter that measures total heat output (μW) was used to determine total metabolic rate (aerobic and anaerobic) and the cost of feeding (specific dynamic action, SDA) in larval Atlantic cod (Gadus morhua) from hatching to 4 weeks post-hatch at 10°C. Total heat output increased throughout development from 2.14 μW at first-feeding to 23.72 μW at 4 weeks post-hatch. SDA was determined by comparing the total heat output among unfed larvae and fed larvae simultaneously. Total heat output increased in the first 2 h after feeding with rotifers (Brachionus sp.) and Artemia, remained high for up to 10 h, was significantly higher in fed larvae than in unfed larvae, and ranged from 16.56 μW at first-feeding to 47.84 μW at 4 weeks post-hatch. The differences in total heat output between unfed and fed larvae were 14.42 μW and 24.12 μW, representing an increase in metabolic cost of feeding by a factor of 1.67 over the first 4 weeks of larval life. That the metabolic cost of feeding increased with development and remained elevated suggests that cod larvae allocate a large part of their energy budget to growth in order to meet the demands of their fast growth rates.

Heat and Mass Transfer Analysis of a Pot-in-Pot Refrigerator Using Reynolds Flow Model

2016 ◽  
Vol 8 (3) ◽  
Author(s):  
Ramendra Pandey ◽  
Bala Pesala
Keyword(s):  
Heat Transfer ◽  
Mass Transfer ◽  
Ambient Temperature ◽  
Heat And Mass Transfer ◽  
Heat Load ◽  
Radiation Heat Transfer ◽  
Ambient Air ◽  
Total Heat ◽  
Maximum Efficiency ◽  
Radiation Heat

Heat and mass transfer analysis of evaporative cooling process in a pot-in-pot cooling system is done based on Reynolds flow hypotheses. The model proposed herein assumes that the heat transfer due to natural convection is coupled with an imaginary ambient air mass flow rate (gAo) which is an essential assumption in order to arrive at the solution for the rate of water evaporation. Effect of several parameters on the pot-in-pot system performance has been studied. The equations are iteratively solved and detailed results are presented to evaluate the cooling performance with respect to various parameters: ambient temperature, relative humidity (RH), pot height, pot radius, total heat load, thermal and hydraulic conductivity, and radiation heat transfer. It was found that pot height, pot radius, total heat load, and radiation heat transfer play a critical role in the performance of the system. The model predicts that at an ambient temperature of 50 °C and RH of 40%, the system achieves a maximum efficiency of 73.44% resulting in a temperature difference of nearly 20 °C. Similarly, for a temperature of 30 °C and RH of 80%, the system efficiency was minimum at 14.79%, thereby verifying the usual concept that the pot-in-pot system is best suited for hot and dry ambient conditions.

Optimal Aerogravity-Assist Trajectories Minimizing Total Heat Load

2017 ◽  
Vol 40 (10) ◽  
pp. 2699-2703 ◽  
Author(s):  
Peter J. Edelman ◽  
James M. Longuski
Keyword(s):  
Heat Load ◽  
Total Heat

Falling Film Evaporation of Water on Horizontal Configured Tube Bundles

2010 ◽  
Author(s):  
Wei Li ◽  
Xiaoyu Wu ◽  
Zhong Luo
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Heat Transfer Enhancement ◽  
Inlet Temperature ◽  
Falling Film ◽  
Transfer Enhancement ◽  
Transfer Coefficients ◽  
Film Evaporation ◽  
Tube Bundles ◽  
Falling Film Evaporation

This paper reports an experimental study on falling film evaporation of water on 6-row horizontal configured tube bundles in a vacuum. Three types of configured tubes, Turbo-CAB-19fpi and −26fpi, Korodense, including smooth tubes for reference, were tested in a range of film Reynolds number from about 10 to 110. Results show that as the falling film Reynolds number increases, falling film evaporation goes from tubes partial dryout regime to fully wet regime; the mean heat transfer coefficients reach peak values in the transition point. Turbo-CAB tubes have the best heat transfer enhancement of falling film evaporation in both regimes, but Korodense tubes’ overall performances are better when tubes are fully wet. The inlet temperature of heating water has hardly any effects on the heat transfer, but the evaporation pressure has controversial effects. A correlation with errors within 10% was also developed to predict the heat transfer enhancement capacity.

The Effect of Net-Type Spacer on the Performance of Direct Contact Membrane Distillation System for Seawater Desalination: Heat and Mass Transfer Analysis

2019 ◽  
Author(s):  
Anas M. Alwatban ◽  
Ahmed M. Alshwairekh ◽  
Umar F. Alqsair ◽  
Abdullah A. Alghafis ◽  
Alparslan Oztekin
Keyword(s):  
Reynolds Number ◽  
Direct Contact ◽  
Concentration Polarization ◽  
Three Dimensional ◽  
Turbulence Models ◽  
Membrane Distillation ◽  
Inlet Temperature ◽  
Vapor Permeation ◽  
Direct Contact Membrane Distillation ◽  
Distillation System

Abstract This work aims to study the effects of the net-type spacer on the performance of direct contact membrane distillation (DCMD) modules. Laminar and k-ω SST turbulence models are used to conduct simulations in three-dimensional modules with and without spacers. The spacers are placed in the middle of the feed and permeate channel. The net type spacers of diameter 0.25h and 0.5h were considered, where h is the height of each channel. The inlet temperature of the feed and the permeate channel set to 353 K and 293 K. The feed Reynolds number is varied (500, 1500) while the permeate Reynolds number is fixed at 330. We revealed that the presence of spacer in the flow channels mitigates both the temperature and the concentration polarization and yields higher vapor permeation. We also showed that the module containing larger size spacers yields better flux performance and lower level of temperature and concentration polarization. Moreover, the modules containing spacers become more efficient as the feed flow rate is increased.

Raised Floor Hybrid Cooled Data Center: Effect on Rack Inlet Air Temperatures When In Row Cooling Units are Installed Between the Racks

2015 ◽  
Author(s):  
Tianyi Gao ◽  
James Geer ◽  
Russell Tipton ◽  
Bruce Murray ◽  
Bahgat G. Sammakia ◽  
...  
Keyword(s):  
Flow Rate ◽  
Data Center ◽  
Heat Load ◽  
Data Centers ◽  
Cooling System ◽  
Air Flow ◽  
Inlet Temperature ◽  
Air Flow Rate ◽  
Air Temperatures ◽  
Cooling Unit

The heat dissipated by high performance IT equipment such as servers and switches in data centers is increasing rapidly, which makes the thermal management even more challenging. IT equipment is typically designed to operate at a rack inlet air temperature ranging between 10 °C and 35 °C. The newest published environmental standards for operating IT equipment proposed by ASHARE specify a long term recommended dry bulb IT air inlet temperature range as 18°C to 27°C. In terms of the short term specification, the largest allowable inlet temperature range to operate at is between 5°C and 45°C. Failure in maintaining these specifications will lead to significantly detrimental impacts to the performance and reliability of these electronic devices. Thus, understanding the cooling system is of paramount importance for the design and operation of data centers. In this paper, a hybrid cooling system is numerically modeled and investigated. The numerical modeling is conducted using a commercial computational fluid dynamics (CFD) code. The hybrid cooling strategy is specified by mounting the in row cooling units between the server racks to assist the raised floor air cooling. The effect of several input variables, including rack heat load and heat density, rack air flow rate, in row cooling unit operating cooling fluid flow rate and temperature, in row coil effectiveness, centralized cooling unit supply air flow rate, non-uniformity in rack heat load, and raised floor height are studied parametrically. Their detailed effects on the rack inlet air temperatures and the in row cooler performance are presented. The modeling results and corresponding analyses are used to develop general installation and operation guidance for the in row cooler strategy of a data center.

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