Numerical analyses of the concentrated solar receiver pipes with superheated steam

Trigeneration plants (TGP) desired for combined production of electricity, heat and refrigeration are highly flexible to follow current loading. But their highest efficiency might be possible only when heat production coincides with its consumption, which is generally impossible in traditional TGP with applying the absorption lithium-bromide chiller (ACh) converting the heat, released from combustion engine in the form of hot water, into refrigeration. Usually, the excessive heat of hot water, not consumed by ACh, is removed to the atmosphere through emergency radiator. However, the well-known methods of TGP efficiency assessment do not consider those heat losses and give the overestimated magnitudes of efficiency for conventional TGP with ACh. The application of booster ejector chiller (ECh), as an example, for utilization of the residual waste heat, remained from ACh and evaluated about 25%, has been proposed to produce supplementary refrigeration for cooling cyclic air of driving combustion engine to increase its electrical efficiency by 3-4 %. In the case of using the supplementary refrigeration for technological or other needs the heat efficiency of TGP will increase to about 0.43 against 0.37 for typical TGP with ACh as example. The new modified criteria to assess a real efficiency of conventional TGP, based on ACh, are proposed which enable to reveal the way of its improvement through minimizing the heat waste. Such combined two-stage waste heat recovery system of TGP can be considered as the alternative to the use of back-up gas boiler to pick up the waste heat potential for conversion by ACh to meet increased refrigeration needs.

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Innovative approaches and modified criteria to improve a thermodynamic efficiency of trigeneration plants

Radchenko,

Forduy

et al. 2024

“…A general way to increase the efficiency of power plants is to utilize the exhaust heat [1][2][3] and cool the working fluid [4] to provide favorable conditions for their efficient operation by application of waste heat recovery chillers [5,6] or electrically driven vapor compression refrigeration machines as in air conditioning system [7,8]. The air is a general working fluid in the majority of the power plants based on combustion engines, in particular, gas turbines [9,10], internal combustion engines [11,12], as well as in air conditioning systems as subsystems which provide processing (cooling) engine intake air or as autonomous systems in stationary [13][14][15] and transport application [16,17].…”

Section: Literature Reviewmentioning

confidence: 99%

Research of hydrodynamic processes in the flow part of a low-flow thermopressor

Konovalov,

Kobalava,

Radchenko

et al. 2024

This research explores the hydrodynamic processes within the flow section of a low-flow thermopressor as a jet-type heat exchanger that utilizes the instantaneous evaporation of highly dispersed liquid in accelerated superheated gas flow resulting in reducing gas temperature with minimum resistance losses in contrast to conventional surface heat exchanger. The efficiency of thermopressor, as a contact heat exchanger, is highly dependent on the design of the flow section and the water injection nozzle. Geometric characteristics perform a crucial role in shaping gas-dynamic processes along the length of the thermopressor's flow section, influenced by resistance losses and local resistance in the tapering and expanding channel segments. Therefore, the optimum thermopressor design has to ensure minimize pressure losses. Using Computational Fluid Dynamics (CFD), the prototype thermopressor models were simulated and the results were compared with experimental data. The empirical equations for local resistance coefficients of thermopressor diffuser and confuser were received to evaluate the impact of various design parameters. The obtained local resistance coefficients for the confuser ranged from 0.02 to 0.08 and for the diffuser – from 0.08 to 0.32. The practical recommendations on geometric and operating parameters and characteristics for enhancing the efficiency of hydrodynamic processes in thermopressor flow part were given.

“…In a recent paper, Kurt et al, [11] have carried out an exhaustive exploration on pressure drops and temperature variation in parabolic trough solar collector absorber tubes using RNG k-epsilon model in a CFD analysis. In their analysis, the superheated steam has been considered as working fluid.…”

Section: Introductionmentioning

confidence: 99%

Numerical investigations on a triple fluid heat exchanger with helical and sinusoidal coils

MARİAPPAN¹

2023

A modification is made in the existing concentric heat exchanger design to enhance its heat duty. A standard concentric tube heat exchanger is modified by considering two inner tubes with a combination of helical and sinusoidal coils. Numerical studies are performed in this triple fluid heat exchanger to assess its thermal performance by taking into account mass flow rate, fluid temperatures, heat transfer, which are governed by fundamental heat transfer equations. Computational fluid dynamics simulation methodology together with local and element-by-element method is applied with a MatLab computer code. Hot water and milk fluids are used as working fluids in helical and sinusoidal coils, respectively. Cooling water is used as shell side fluid. The attainment of high heat-load-per-unit-area and high surface-area-to-volume ratio is used as optimizing parameter in the simulations. The helical coil provides an increase in heat transfer rate and overall heat transfer coefficient increases by a percentage 13% for varying hot fluid flow rates, when it is compared with the sinusoidal coil. The pressure drop for the helical coil increases, exponentially compared to the sinusoidal coil, thereby it shows a higher pumping power for the helical coil.