Cooling Water Temperature Rise Research Articles

Comparison of dual-pressure organic Rankine cycle using zeotropic mixtures

The dual-evaporation organic Rankine cycle (DORC) using zeotropic mixtures can effectively reduce the irreversible loss both in the evaporator and condenser, and thus improve the net power output compared to the DORC using pure working fluid. This paper investigated the DORC using zeotropic mixtures for recovering low-grade energy. The effects of different condensation temperatures (fixed dew point and fixed bubble point condensation temperature, optimized condensation temperature), temperature glide of zeotropic mixtures and cooling water temperature rise on the net power output of the DORC were investigated. The results indicate that the DORC using zeotropic mixtures under optimal mass fraction can improve the net power output by 6.4–16.6% compared to the DORC using pure working fluid. In selecting the zeotropic mixtures for the DORC, the maximum value of the temperature glide of the zeotropic mixtures under condensation pressure should be larger than the cooling medium temperature increase. The irreversible loss in the evaporator is the most among the four irreversible losses, followed by that in the condenser. However, the effect of irreversible loss in the condenser on the variation trend of the total irreversible loss is the most significant.

An investigation of the second law performance for a condenser used in 210 MW thermal power station

This work presents a case study of thermodynamic performance of a condenser used in a 210 MW thermal power station at Mejia in West Bengal, India. The analysis involves an improvement of actual overall heat transfer coefficient by varying tube materials and fouling resistance. Exergy Destruction Factor (EDF) is introduced to quantify the percentage of exergy loss from the condenser wall. From this study, it is revealed that the second law performance of the condenser increases with the increase in thermal conductivity of the tube materials, decreases with the increase in fouling resistance and decreases with the increase in condenser pressure at the turbine outlet. The actual overall heat transfer coefficient can be increased up to 6% by selecting better conducting tube materials. While the EDF decreases with the increase in cooling water temperature rise and increases with the increase in cooling water inlet temperature, EDF is found to decrease with the increased cooling water mass flow rate.

Mathematical Modeling of Heat Transfer and Deformation of Bloom Tube Mold in Continuous Casting Process

The deformation of a bloom tube mold was investigated using an in-house-developed complex model considering the flow, heat transfer, and solidification as well as the copper tube stress strain. This model was validated by the cooling water temperature rise, solidification shell thickness, copper oxidized zone, and measured copper deformation. Based on this model, the heat transfer characteristics of the mold were analyzed. The deformation trends of the copper tube under different water pressures were compared. The results revealed that the deformation of the wide copper plate was mainly influenced by the cooling water pressure, whereas the deformation on the narrow side was primarily affected by the temperature field. Similarly, the corner distortion of the copper plate resulted mainly from the deformation of the wide and the narrow copper plates.

Thermo-economic performance evaluation of emerging liquid-separated condensation method in single-pressure and dual-pressure evaporation organic Rankine cycle systems

Liquid-separated condensation is an emerging and effective heat transfer enhancement method to reduce the condenser cost, which can help with the widespread application of organic Rankine cycle (ORC) systems. However, few related studies have focused on the shell-and-tube condenser even if it is widely used in ORC systems. The thermo-economic performance superiorities and applicable working conditions of shell-and-tube liquid-separated condenser should be investigated, especially in novel ORCs. This study introduced the liquid-separated condensation method into single-pressure and dual-pressure evaporation ORC systems with shell-and-tube condenser. R245fa, R600a, and R1234ze(E) were used as working fluids. Optimal liquid-separated thermodynamic states and decrements in condenser heat transfer area of one to four stages liquid-separated condensations were provided. Decrements in specific investment cost (SIC) of ORC system by adopting the liquid-separated condensation method were evaluated. Results show that the liquid-separated condensation method is more suitable for low tube diameter, low inlet velocity in tubes, high inlet velocity outside tubes, and low cooling water temperature rise. Optimal liquid-separated thermodynamic states remain constant with increasing the tube diameter and inlet velocities. The SIC of ORC system can be reduced by 4.6% at most by adopting the liquid-separated condensation over the conventional condensation method. Increasing the mass flow rate of heat source fluid and pinch point temperature difference during heat absorption process is beneficial to increase the superiority of liquid-separated condensation method. Compared with dual-pressure evaporation ORC, the effects of liquid-separated condensation method on reducing the SIC are more remarkable in single-pressure evaporation ORC.

Fluid flow and heat transfer behavior of liquid steel in slab mold with different corner structures. Part 2: Fluid flow, heat transfer, and solidification characteristics

ABSTRACTIn this article, the complex transmission behavior was discussed in the slab mold with different corner structures. Results show that the up backflow is stronger than the down backflow. The cooling water temperature rise and heat flux through the wide face in the right-angle mold are the largest, while those through the narrow face in the multichamfered mold are larger than those in the big-chamfered mold. The corner temperature at mold exit of the right-angle, big-chamfered, and multichamfered strand increases. The shell thickness at the narrow face center in the chamfered mold is thinner than that in the right-angle mold.

Fluid flow and heat transfer behavior of liquid steel in slab mold with different corner structures. Part 1: Mathematical model and verification

ABSTRACTA three-dimensional model considering the fluid and temperature field of the liquid steel and cooling water, along with the copper plate temperature was established to study the fluid flow and heat transfer behavior of liquid steel in slab mold with different corner structures. Then, a two-dimensional stress–strain model was established to calculate the strand shrinkage. The two-dimensional stress and three-dimensional temperature were connected through the thermal resistance. The model was validated by the measured solidification shell, copper plate temperature, and cooling water temperature rise. Results show that this model is suitable to study the complex transmission behavior in slab mold.

Optimized liquid-separated thermodynamic states for working fluids of organic Rankine cycles with liquid-separated condensation

Liquid-separated condensation is an emerging enhanced heat transfer method that simultaneously increases the condensation heat transfer coefficient and reduces the pressure drop. This method was applied to shell-and-tube condensers used in organic Rankine cycle systems. The optimized liquid-separated thermodynamic states of organic fluids which maximize the average condensation heat transfer coefficients were studied for the single-stage and two-stage liquid-separated condensations. Effects of the heat exchange tube diameter, organic fluid mass flux and cooling water temperature rise on the optimized liquid-separated thermodynamic states and heat transfer enhancement effects were also analyzed. Results show that the minimized condenser area decreases by 10.2%–18.1% for the single-stage liquid-separated condensation and 14.5%–25.0% for the two-stage, compared to the conventional condensation. Optimized liquid-separated thermodynamic states of nine organic fluids were also obtained. Reducing the heat exchange tube diameter, organic fluid mass flux and cooling water temperature rise, the decrement in the condenser area increases. Increasing the liquid-separation stage is beneficial for reducing the condenser area. The optimized vapor quality at the liquid-separated unit inlet remains constant as the heat exchange tube diameter and organic fluid mass flux decrease. While, it decreases as the cooling water temperature rise decreases.

The Exergy Loss Distribution and the Heat Transfer Capability in Subcritical Organic Rankine Cycle

Taking net power output as the optimization objective, the exergy loss distribution of the subcritical Organic Rankine Cycle (ORC) system by using R245fa as the working fluid was calculated under the optimal conditions. The influences of heat source temperature, the evaporator pinch point temperature difference, the expander isentropic efficiency and the cooling water temperature rise on the exergy loss distribution of subcritical ORC system are comprehensively discussed. It is found that there exists a critical value of expander isentropic efficiency and cooling water temperature rise, respectively, under certain conditions. The magnitude of critical value will affect the relative distribution of exergy loss in the expander, the evaporator and the condenser. The research results will help to better understand the characteristics of the exergy loss distribution in an ORC system.

Analysis of organic Rankine cycles using zeotropic mixtures as working fluids under different restrictive conditions

Organic Rankine cycle has been regarded as a reasonable technology to utilize low-temperature geothermal sources. This paper analyzes the internal relation about zeotropic mixture selection under different restrictive conditions. R601a/R600 and R245fa/R600a are selected as typical examples of symmetrical and asymmetric zeotropic mixtures. The fixed condenser bubble temperature, the fixed cooling water temperature rise and the fixed cooling water flow rate are considered as restrictive conditions. Both the basic and the regenerative organic Rankine cycle system are considered as research subjects. The fixed cooling water flow rate is suggested to select the appropriate zeotropic mixture. The results indicate that the performance corves with the fixed condenser bubble temperature of 25°C are significant in zeotropic mixture selection, and these corves reflect the full potential of zeotropic mixtures to improve the net power. The temperature glide decreases the net power with the fixed condenser bubble temperature. However, the opposite phenomenon is found when the fixed cooling water temperature rise or the fixed cooling water flow rate is applied. The application of intermediate heat exchangers may lead to the larger, the smaller or the same net power with different temperature glides and restrictive conditions. However, the cycle efficiency is increased all the time.

Analysis and optimization of heat loss for water-cooled furnace roller

A heat transfer model of furnace roller cooling process was established based on analysis of furnace roller’s structure. The complicated model was solved with iteration planning algorithm based on Newton search. The model is proved logical and credible by comparing calculated results and measured data. Then, the relationship between water flow velocity, inlet water temperature, furnace temperature and roller cross section temperature, outlet water temperature, water temperature rise, cooling water heat absorption was studied. The conclusions and recommendations are mainly as follows: 1) Cooling water temperature rise decreases with the increase of water flow velocity, but it has small relationship with inlet water temperature; 2) In order to get little water scale, inlet water temperature should be controlled below 30 °C. 3) The cooling water flow velocity should be greater than critical velocity. The critical velocity is 0.07 m/s and water flow velocity should be controlled within 0.4–0.8 m/s. Within this velocity range, water cooling efficiency is high and water temperature rise is little. If cooling water velocity increases again, heat loss will increase, leading to energy wasting.

Analysis of the Cooling Water Temperature Rise of Accelerating Electrodes in EAST Neutral Beam Injector Beam Extraction

Neutral beam injection is recognized as one of the most effective means of plasma heating. The preliminary data of beam power deposition in different electrodes during beam extraction are obtained on the EAST neutral beam injector test stand. The measurement of the cooling water temperature rise of accelerating electrodes is reported. The data given can guide the optimization of beam extraction parameters and decrease the damage to the accelerating electrodes following long pulse beam extraction.

Preliminary design of a university laboratory hybrid rocket engine

This paper gives an overview of the preliminary design of a small hybrid rocket engine (HRE) that is being built in support of propulsion research activities at Ryerson University. The initial design work was undertaken primarily with a paraffin and gaseous oxygen (GOx) propellant combination in mind, but the system is readily adaptable to other propellant combinations for future investigations. When a reusable, non-eroding nozzle is necessary for accurate engine performance measurements, a water-cooled copper design is to be employed. This approach offers the added benefit of allowing the cooling water temperature rise to be measured, and thus the amount of heat being handled by the nozzle can be quantified. The preliminary nozzle design is supported by a steady-state computational fluid dynamics (CFD) analysis of the nozzle flows and associated heat fluxes. The overall engine design is further evaluated by examination of internal ballistic simulation results with respect to such factors as expected performance (chamber pressure, thrust, specific impulse, and total impulse) for a given oxidizer mass flow rate and nozzle throat size.

Initial long-pulse plasma heating at reduced power with negative-ion-based neutral beam injector in large helical device

We have achieved long-pulse plasma heating using a negative-ion-based neutral beam injector (NBI) in the large helical device (LHD), where the confinement magnetic field is generated by only external superconducting coils. In the initial long-pulse experiments at lower power than that in short-pulse experiments, 80 keV–1.1 MW NBI heating lasted for 10 s with a little increase in the plasma density at the pulse end. Almost steady-state plasma heating was achieved for 21 s with 66 keV–0.6 MW NB injection. Plasma relaxation oscillation phenomena at a period of 1–2 s were also observed for 20 s. Above 1 keV plasma was easily sustained with a long-pulse NBI heating in LHD, without the current drive nor the disruption in tokamaks. Negative ion source operation was stable and the cooling water temperature rise of beam accelerator grids was nearly saturated with a temperature rise below 10 °C. For a higher power injection, the pulse duration is determined by the beam blocking, where the reionization loss is exponentially increased together with an increase in outgas in the injection port. The port conditioning by a careful repetition of injection is effective to the extension of the injection duration and the plasma maintenance duration. The initial long-pulse NBI heating at the reduced power has demonstrated an ability of steady-state operation in superconducting LHD.

97/04995 Use of coal fly ash for ceramics: a case study for a large Spanish power station: Queralt, I. et al. Fuel, 1997, 76, (8), 787–791

Organic Rankine cycle has been regarded as a reasonable technology to utilize low-temperature geothermal sources. This paper analyzes the internal relation about zeotropic mixture selection under different restrictive conditions. R601a/R600 and R245fa/R600a are selected as typical examples of symmetrical and asymmetric zeotropic mixtures. The fixed condenser bubble temperature, the fixed cooling water temperature rise and the fixed cooling water flow rate are considered as restrictive conditions. Both the basic and the regenerative organic Rankine cycle system are considered as research subjects. The fixed cooling water flow rate is suggested to select the appropriate zeotropic mixture. The results indicate that the performance corves with the fixed condenser bubble temperature of 25 °C are significant in zeotropic mixture selection, and these corves reflect the full potential of zeotropic mixtures to improve the net power. The temperature glide decreases the net power with the fixed condenser bubble temperature. However, the opposite phenomenon is found when the fixed cooling water temperature rise or the fixed cooling water flow rate is applied. The application of intermediate heat exchangers may lead to the larger, the smaller or the same net power with different temperature glides and restrictive conditions. However, the cycle efficiency is increased all the time.