scholarly journals Economic justification of the choice of the thermal protection of buildings

2018 ◽  
Vol 196 ◽  
pp. 04078
Author(s):  
Elena Malyavina ◽  
Anastasya Frolova
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Specific Heat ◽  
Thermal Protection ◽  
Transfer Resistance ◽  
Cooling Systems ◽  
Heating And Cooling ◽  
Heat Protection ◽  
The Cost

A large number of factors influence the economically feasible heat transfer resistance of the building enclosing structures. First of all, it is the cost of insulation and heat for the building heating in the cold season. As shown by studies, it is not enough for air-conditioned buildings. The result depends on the mode of the building operation in time and the heat load on the heating and cooling systems. Therefore, in addition to these significant factors of economic feasibility of the thermal protection level, there are the cost of electricity for the production of cold for cooling the building, the cost of the building heating and cooling systems and the cost of connection to power supply networks. The got result is important to convey to the professional community in a clear and compact form. In the present work the buildings of administrative and office purpose are considered, the working day of which lasts from 9-00 to 18-00 hours with different specific heat supply from 0 to 80 W/m2 on the estimated area during working hours. Generalization of the research results is made on the basis of specific heat protection characteristics of the building, which is a product of the overall heat transfer coefficient of the building and the compactness coefficient. The total heat transfer coefficient of the building characterizes the heat losses and the heat inflows to the building through the enclosing structures, and the compactness coefficient can serve as an indicator of the surface area of the building, which is covered with insulation. For these buildings provision has been made for identification of the areas of the total discounted cost combination for all of the above components and the specific heat protection characteristics of the building relating to the feasibility of the specified level of the thermal protection.

Efficiency Centered Maintenance of Preheat Train of a Crude Oil Distillation Unit

2020 ◽  
Author(s):  
J. Fajardo ◽  
D. Yabrudy ◽  
D. Barreto ◽  
C. Negrete ◽  
B. Sarria ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Energy Efficiency ◽  
Heat Transfer Coefficient ◽  
Heat Exchanger ◽  
Transfer Coefficient ◽  
Operational Reliability ◽  
Distillation Unit ◽  
Maintenance Costs ◽  
Oil Refineries ◽  
The Cost

Abstract Nowadays, maintenance is based on the synergistic integration of operational reliability and timely maintenance, which guarantees the required availability and optimal cost. Operational reliability implies producing more, better performance, longer life, and availability. Timely maintenance involves the least time out of service, fewer maintenance costs, fewer operating costs, and less money. In this work, we study the preheating train of a crude distillation unit of a refinery, which processes 994 m3/h, which presents a formation of a fouling layer inside it. Among the impacts of fouling is the reduction in the effectiveness of heat transfer, the increase in fuel consumption, the increase in CO2 emissions, the increase in maintenance costs, and the decrease in the profit margin of process. An appropriate cleaning program of the surface of the heat exchanger network is necessary to preserve its key performance parameters, preferably close to design values. This paper presents the maintenance method centered on energy efficiency, to plan the intervention of the preheating train equipment maintenance, which considers the economic energy improvement and the cost of the type of maintenance. The method requires the calculation of the fouling evolution from which the global heat transfer coefficient is obtained, and the heat flux is determined as a function of time. It was observed that, as time passes, the resistance provided by fouling increases and that the overall heat transfer coefficient decreases. The energy efficiency centered maintenance has an indicator of economic justification (factor J) that relates the economic-energy improvement achieved when performing maintenance, taking into account the economic effort invested. Depending on the cost of the type of maintenance to be performed, a threshold should be chosen, from which the maintenance activity is justified. The effectiveness values of the heat exchanger (ε) and the J indicator are used to form a criticality matrix, which allows prioritizing maintenance activities in each equipment. The planning of the implementation dates of the maintenance of each heat exchanger, from the maintenance method centered on energy efficiency applied to the crude distillation unit’s, preheat train, constitutes a contribution in this specific field. The conceptual design of the maintenance method centered on energy efficiency presented in this work is feasible for other heat transfer equipment used in oil refineries and industry in general. The procedure developed uses real operation values, and with its implementation, a saving of 150000 US dollars was achieved.

Forced Convection Heat Transfer of Nanofluids: A Review

2017 ◽  
Author(s):  
Aditya Kuchibhotla ◽  
Debjyoti Banerjee
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Thermal Conductivity ◽  
Heat Capacity ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Specific Heat ◽  
Forced Convection ◽  
Convection Heat Transfer ◽  
Convection Heat

Stable homogeneous colloidal suspensions of nanoparticles in a liquid solvents are termed as nanofluids. In this review the results for the forced convection heat transfer of nanofluids are gleaned from the literature reports. This study attempts to evaluate the experimental data in the literature for the efficacy of employing nanofluids as heat transfer fluids (HTF) and for Thermal Energy Storage (TES). The efficacy of nanofluids for improving the performance of compact heat exchangers were also explored. In addition to thermal conductivity and specific heat capacity the rheological behavior of nanofluids also play a significant role for various applications. The material properties of nanofluids are highly sensitive to small variations in synthesis protocols. Hence the scope of this review encompassed various sub-topics including: synthesis protocols for nanofluids, materials characterization, thermo-physical properties (thermal conductivity, viscosity, specific heat capacity), pressure drop and heat transfer coefficients under forced convection conditions. The measured values of heat transfer coefficient of the nanofluids varies with testing configuration i.e. flow regime, boundary condition and geometry. Furthermore, a review of the reported results on the effects of particle concentration, size, temperature is presented in this study. A brief discussion on the pros and cons of various models in the literature is also performed — especially pertaining to the reports on the anomalous enhancement in heat transfer coefficient of nanofluids. Furthermore, the experimental data in the literature indicate that the enhancement observed in heat transfer coefficient is incongruous compared to the level of thermal conductivity enhancement obtained in these studies. Plausible explanations for this incongruous behavior is explored in this review. A brief discussion on the applicability of conventional single phase convection correlations based on Newtonian rheological models for predicting the heat transfer characteristics of the nanofluids is also explored in this review (especially considering that nanofluids often display non-Newtonian rheology). Validity of various correlations reported in the literature that were developed from experiments, is also explored in this review. These comparisons were performed as a function of various parameters, such as, for the same mass flow rate, Reynolds number, mass averaged velocity and pumping power.

Cooling Optimization Theory—Part II: Optimum Internal Heat Transfer Coefficient Distribution

2016 ◽  
Vol 138 (8) ◽  
Author(s):  
Benjamin Kirollos ◽  
Thomas Povey
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Flow Rate ◽  
Wall Temperature ◽  
Internal Heat ◽  
Cooling Systems ◽  
Uniform Wall Temperature ◽  
Uniform Wall ◽  
Internal Heat Transfer

Gas turbine cooling system design is constrained by a maximum allowable wall temperature (dictated by the material, the life requirements of the component, and a given stress distribution), the desire to minimize coolant mass flow rate (requirement to minimize cycle-efficiency cost), and the requirement to achieve as close to uniform wall temperature as possible (to reduce thermal gradients, and stress). These three design requirements form the basis of an iterative design process. The relationship between the requirements has received little discussion in the literature, despite being of interest from both a theoretical and a practical viewpoint. In Part I, we show analytically that the coolant mass flow rate is minimized when the wall temperature is uniform and equal to the maximum allowable wall temperature. In this paper, we show that designs optimized for uniform wall temperature have a corresponding optimum internal heat transfer coefficient (HTC) distribution. In this paper, analytical expressions for the optimum internal HTC distribution are derived for a number of cooling systems, with and without thermal barrier coating (TBC). Most cooling systems can be modeled as a combination of these representative systems. The optimum internal HTC distribution is evaluated for a number of engine-realistic systems: long plate systems (e.g., combustors, afterburners), the suction-side (SS) of a high pressure nozzle guide vane (HPNGV), and a radial serpentine cooling passage. For some systems, a uniform wall temperature is unachievable; the coolant penalty associated with this temperature nonuniformity is estimated. A framework for predicting the optimum internal HTC for systems with any distribution of external HTC, wall properties, and film effectiveness is outlined.

Cooling Optimisation Theory: Part 2 — Optimum Internal Heat Transfer Coefficient Distribution

2015 ◽  
Author(s):  
Benjamin Kirollos ◽  
Thomas Povey
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Flow Rate ◽  
Wall Temperature ◽  
Internal Heat ◽  
Cooling Systems ◽  
Uniform Wall Temperature ◽  
Uniform Wall ◽  
Internal Heat Transfer

Gas turbine cooling system design is constrained by a maximum allowable wall temperature (dictated by the material, the life requirements of the component and a given stress distribution), the desire to minimise coolant mass flow rate (requirement to minimise cycle-efficiency cost) and the requirement to achieve as close to uniform wall temperature as possible (to reduce thermal gradients, and stress). These three design requirements form the basis of an iterative design process. The relationship between the requirements has received little discussion in the literature, despite being of interest from both a theoretical and a practical viewpoint. In the companion paper, we show analytically that the coolant mass flow rate is minimised when the wall temperature is uniform and equal to the maximum allowable wall temperature. In this paper, we show that designs optimised for uniform wall temperature have a corresponding optimum internal heat transfer coefficient (HTC) distribution. In this paper, analytical expressions for the optimum internal HTC distribution are derived for a number of cooling systems, with and without thermal barrier coating. Most cooling systems can be modelled as a combination of these representative systems. The optimum internal HTC distribution is evaluated for a number of engine-realistic systems: long plate systems (e.g., combustors, afterburners), the suction-side of a high pressure nozzle guide vane, and a radial serpentine cooling passage. For some systems, a uniform wall temperature is unachievable; the coolant penalty associated with this temperature non-uniformity is estimated. A framework for predicting the optimum internal HTC for systems with any distribution of external HTC, wall properties and film effectiveness is outlined.

Film Cooling Performance of Converging-Slot Holes With Different Exit-Entry Area Ratios

2009 ◽  
Author(s):  
Cun-liang Liu ◽  
Hui-ren Zhu ◽  
Jiang-tao Bai ◽  
Du-chun Xu
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Film Cooling ◽  
Thermal Protection ◽  
Area Ratio ◽  
Cooling Effectiveness ◽  
Momentum Ratio ◽  
Film Cooling Effectiveness ◽  
Distribution Features

Film cooling performances of two kinds of converging slot-hole (console) with different exit-entry area ratios have been measured using a new transient liquid crystal measurement technique which can process the nonuniform initial wall temperature. Four momentum ratios are tested. The film cooling effectiveness distribution features are similar for the two consoles under all the momentum ratios. Consoles with smaller exit-entry area ratio produce higher cooling effectiveness. And the laterally averaged cooling effectiveness results show that the best momentum ratio for both consoles’ film cooling effectiveness distribution is around 2. For both consoles, the heat transfer in the midspan region is stronger than that in the hole centerline region in the upstream, but gradually becomes weaker as flowing downstream. With the momentum ratio increasing, the normalized heat transfer coefficient h/ho of both consoles increases. In the upstream, heat transfer coefficient of console with small exit-entry area ratio is higher. But in the downstream, the jets’ turbulence and the couple vortices play notable elevating effect on the heat transfer coefficient for large exit-entry area ratio case, especially under small momentum ratios. Consoles with smaller exit-entry area ratio provide better thermal protection because of higher cooling effectiveness. And the distributions of heat flux ratio are similar with those of cooling effectiveness because the influence of η on q/q0 is larger. For the consoles, smaller exit-entry area ratios produce lower discharge coefficients when the pressure variation caused by the hole shaped is regarded as flow resistant.

scholarly journals Field Study on the Air-Side Heat Transfer Performance of Copper Finned-Flat Tubes for Heavy-Duty Truck Radiators

2021 ◽  
Vol 39 (5) ◽  
pp. 1451-1459
Author(s):  
Jose Canazas
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Transfer Rate ◽  
Heat Transfer Performance ◽  
Transfer Performance ◽  
Heavy Duty ◽  
Cooling Systems ◽  
Heavy Duty Truck ◽  
Flat Tubes

Heavy-duty truck cooling systems have been given low importance in the enhancement and research of heat transfer performance since off-highway conditions are hard to evaluate in laboratory essays or CFD studies. The present work is performed to evaluate the heat transfer performance of copper finned-flat tubes used in heavy-duty truck radiators. Parameters were measured in the field of two heavy-duty truck engines cooling systems. In both vehicles water is used as the cooling fluid. The results showed that the Air convective heat transfer coefficient and Overall heat transfer coefficient on the air side decreases as the Reynolds Number decreases and increases as passing through the first row to the fourth row. Additionally, the mass air flow and heat transfer rate have very high values in comparison from normal automotive radiators' operative conditions, since heavy-duty truck radiators require a large heat transfer rate. The analysis presented in this paper was used for a heavy-duty truck radiator but can be extended to any equipment with finned flat tubes. A more accurate study should be done considering vibrations and different environmental conditions.

Conjugate Heat Transfer Analysis of Circular Microtube Under Time Varying Heat Source

2005 ◽  
Author(s):  
Abdullatif A. Gari ◽  
Muhammad M. Rahman
Keyword(s):  
Magnetic Field ◽  
Heat Transfer ◽  
Magnetic Material ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Transient Heat Conduction ◽  
Heat Transfer Analysis ◽  
Working Fluid ◽  
Heating And Cooling ◽  
The Magnetic Field

When a magnetic field is applied to a magnetic material it releases energy. It has been proven experimentally that this temperature rise could be as high as 20 K when a magnetic field of 10 T is applied. Heat is generated when the magnetic field is applied and cooling is produced when the magnetic field is released. The purpose of this study is to explore transient heat transfer coefficient when a fluid is circulated in the substrate through microchannels. Equations for the conservation of mass, momentum, and energy were solved in the fluid region. In the solid region, the transient heat conduction equation was solved. Gadolinium and water were picked as the magnetic material and working fluid respectively. The results are represented by plotting the variations of heat transfer coefficient and Nusselt number with time at various sections of the tube. The effects of the magnetic field strength, diameter of the microtube in the substrate, and Reynolds number were studied. It was found that the heat transfer coefficient changes with time in a periodic fashion when heating and cooling are generated in the system by repeated introduction and relaxation of the magnetic field. The results of this study will be useful for the development of microtube heat exchangers for a compact magnetic refrigerator.

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