This chapter contains sections titled:
Introduction
Equipment Description
Describing Equations
The “F” Factor
Effectiveness Factor and Number of Transfer Units
References
The effect of a radial d.c. electric field on nucleate boiling heat transfer was investigated experimentally using a single-tube shell/tube heat exchanger. A dielectric liquid (Freon R. 114) was used ...in the shell and the tube was heated by circulating water through it.
It was found that the application of a sufficiently intense electric field to the boiling heat transfer surface resulted both in the elimination of boiling hysteresis and the enhancement of heat transfer for the range of superheat studied. An application of approximately 20 kV was more than sufficient to eliminate the hysteresis.
It was also observed that there appeared to be a transition between two situations. At lower superheat there is an appreciable improvement in the heat transfer coefficient due to both initial (0 to 10 kV) and incremental (10 to 20 kV) voltage increases. At higher superheat, however, the greater improvement (about four times) is obtained with the initial voltage application
The experimental parametric investigation on a vapour condenser under vacuum conditions for the vacuum drying application has been presented. The mixture of air-vapour and the non-condensates are ...extracted from the system using a vacuum condenser. Hence, the vapour's behaviour inside a condenser becomes a subject of study exposed to different operating conditions. In the current study, parameters considered are condenser pressure (20 and 70 mbar), inlet valve orifice diameter (10 and 8 mm), and the cooling water flow rate through the pipes (32 lpm and 16 lpm). The condensation rate increases with the shell pressure and seems to remain unaffected by the chilling water flow rates. The turbulence in the steam flow increases with the increase in the shell pressure. The fluids flowing through tubes at low-velocity experience smaller pressure drops and show low heat transfer coefficients. The reproducibility and repeatability of the tests are excellent.
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S277.9; A study on heat transfer performance by thermal fluid coupling simulation for the fouling in a shell-tube heat exchanger used in engineering was presented.The coupling simulation was ...performed in a fluid and solid domains under three different fouling conditions:fouling inside the tube,fouling outside the tube,and fouling inside the shell.The flow field,temperature,and pressure distributions in the heat exchanger were solved numerically to analyze the heat transfer performance parameters,such as thermal resistance.It is found that the pressure drop of the heat exchanger and the thermal re-sistance of the tube wall increase by nearly 30％and 20％,respectively,when the relative fouling thickness reaches 10％.The fouling inside the tube has more impact on the heat transfer performance of the heat exchanger,and the fouling inside the shell has less impact.
•Fatigue failure of welded joints in a shell-tube heat exchanger was analyzed.•Fatigue crack initiated from the defects at the tube-to-tubesheet welded joint.•Bad welding and unsuitable expansion ...gave rise to the formation of initial cracks.•The alternating stress comes from various reasons such as the resonant vibration.
Failure analysis was carried out on a tube-to-tubesheet welded joint of a shell-tube heat exchanger to confirm its failure mechanism. The collected evidence suggests that the failure of the tube-to-tubesheet welded joint was induced by fatigue. Under the morphology analysis, the fracture surface exhibit obvious fatigue crack propagation traces. Fatigue striations were observed clearly in the propagation zone. Detecting results showed that chemical composition and mechanical properties of the tubes was consistent with the standard requirements for the 304 stainless steel. The metallographic test showed that the microstructure of both the tube and tubesheet were normal. However, serious defects were found at the tube-to-tubesheet welded joint. The fatigue crack initiated from the defects at the tube-to-tubesheet welded joint. The periodic load might come from the resonant vibration of the tube or the changes in temperature and pressure of the fluid inside the heat exchanger. Bad welding and unsuitable expansion position of the tubes at the tube-to-tubesheet might give rise to the formation of initial cracks.
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District heating has been widely implemented in residences because of its environmental and economic advantages. The hot water load of residences generally peaks in the morning and at night because ...of the lifestyle of the residents. An imbalance in the heat load presents high capital costs and low operating efficiency of the district heating facilities. In this study, a latent heat storage system using a solid-liquid phase change material was developed for the peak load shifting control of hot water supplied from district heating in an apartment complex. The latent heat storage system was designed using a shell-tube structure and can store heat for more than 100 h using an insulation of 50 mm. A field demonstration was performed by installing the developed latent heat storage system in a machinery room in the basement of the apartment complex. The demonstration showed that the total heat flow of hot water during a day and its standard deviation with the latent heat storage are lower than those without latent heat storage by 2.69% and 59.9%, respectively. Therefore, the latent heat storage system is crucial in the peak load shifting of hot water in the apartment complex.
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Abstract
The baffle plate is the most important elements affecting not only the thermal efficiency but also the hydraulic performance of shell-tube heat exchangers that can be designed in different ...types today and can be put into the production phase. Different designs of baffle plates are closely related to thermal performance with pressure drop as well. In this investigation, the design geometry of the shell-tube type was carried out by means of the ANSYS Fluent program.
In the analyses, it is purposed to examine the consequences on the heat transfer rate per drop of pressure and not only the pressure’s drop but also the coefficient parameter of heat transfer of the exchangers in which traditional one-piece type baffle plate and perforated type baffle plate are used where the shell side. Here, water is used as the working fluid; it was examined as 1.2, 1.5, 1.8 and 2.1 kg/h at four varied mass flow rates (m). As a result, the values compared to the traditional one-piece baffle plate and the perforated type baffle plate. It has been monitored that the heat transfer rates per drop of pressure vary.
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•Using flow hydraulic network model is an alternative design method.•NTW design technique improve the original design heat transfer performance.•Reduce the original design pressure drop by removing ...window-section tubes.•NTW design technique reduce the original design exergy destruction rate.
In the present study, performance analysis of a shell-tube heat exchanger by using hydraulic network modeling has been employed in order to enhance the performance of the heat exchanger. Since a major component of a shell-tube heat exchanger is tubes, the aim of this paper is to study the effect of using different tube count, tube layout and tube diameter at different baffle sections on heat transfer, pressure losses and exergy destruction rate of shell-tube heat exchangers with segmental baffles. Three different modified designs with a classical design of a specimen shell-tube heat exchanger have been taken into consideration for their thermo-hydraulic performances and the results are compared. It is revealed that the modified heat exchanger, even though the number of tubes is reduced compared to the conventional design version, has better thermo-hydraulic performance, improving the original design heat transfer performance, and having lower exergy destruction rate. Eliminating window section will allow the cross and window flow to mix better and will automatically increase the heat transfer performance. The results obtained from the present method show that by elimination window-section baffles, heat transfer performance (hs/ΔPs) increased about 25–48% at different mass flow rates. Also for a shell-tube heat exchanger requiring low pressure drop No Tube at Window section design (NTW) is an alternative. So application of NTW shell-tube heat exchangers is recommended and the results of these methods are directly applicable to real design. Also using this method provides the necessary database to refine the previous empirical flow rate methods for use in the prediction of the instabilities of industrial heat exchanger tube bundles.
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•Literature review on void-fraction correlations of two-phase flow in tube bundles and available data for cross-flow in horizontal tube bundles has been performed.•The criticality of the hydraulic ...diameter in a sub-channel of horizontal tube bundles has been addressed to distinguish the channel average and gap average mass velocity.•Development methodology of the newly drift-flux correlation for upward two-phase cross-flow horizontal tube bundles has been performed.•Comparison of the newly drift-flux correlation with experimental data as well as the error analysis have been presented.•A full range drift-flux correlation has been developed based on interpolation scheme.
In relation to void fraction prediction of cross-flow in horizontal tube bundle of shell-tube heat exchangers, a drift-flux correlation has been developed to meet the demand on the study of two-phase flow gas and liquid velocities, two-phase pressure drop, heat transfer, flow patterns and flow induced vibrations in the shell side. Two critical parameters such as distribution parameter and drift velocity have been modeled. The distribution parameter is obtained by constant asymptotic values and taking into account the differences in channel geometry. The drift velocity is modelled depending on the density ratio and the non-dimensional viscosity number. The relationship between the channel averaged and gap mass velocity has been discussed in order to obtain the superficial gas and liquid velocities in the drift-flux correlation. The newly developed drift-flux correlation agrees well with cross-flow experimental databases of air-water, R-11 and R-113 in parallel triangular, normal square and normal triangular arrays with the mean absolute error of 1.06% and the standard deviation of 4.47%. In comparison with other existing correlations, the newly developed drift-flux correlation is superior to other studies due to the improved accuracy. In order to extend the applicability of the newly developed drift-flux correlation to void fraction of unity, an interpolation scheme has been developed. The newly developed drift-flux correlation is able to calculate the void fraction of cross-flow over a full range with different sub-channel configurations in shell-tube type heat exchangers.
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Poultry litter is one type of biomass and waste generated from the farming process. This study performed a performance and process analysis of poultry litter to energy using the lab-scale shell and ...tube heat exchanger (STHE) system along with a Stirling engine and a swirling fluidized bed combustor (SFBC). The effects of tube shape, flow direction, and water flow rates on water and trailer temperature changes were investigated during the poultry litter co-combustion process. Energy flow analysis and emissions were also studied. Results showed that the water outlet temperature of 62.8 ° C in the twisted tube was higher than the straight tube case (58.3 ° C ) after 130 min of the co-combustion process. It was found that the counter-current direction had higher water temperature changes, higher logarithmic mean temperature difference (LMTD), and higher trailer temperature changes than the co-current direction. A water flow rate of 4.54 L/min showed adequate heat absorption in the lab-scale STHE system and heat rejection in the trailer. Results indicated that the lab-scale STHE system has a conversion efficiency of 42.3% and produces hot water (at about 63.9 ° C ) along with lower emissions. This research study confirmed that poultry litter can be used to generate energy (e.g., hot water and electricity) by using a lab-scale biomass conversion system for space heating applications.
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