direct contact heat exchanger
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2021 ◽  
Author(s):  
Wasakorn Treedet ◽  
Ratchaphon Suntivarakorn ◽  
Ilham Mufandi ◽  
Piyapong Singbua

Abstract This article presented an improvement of bio-oil production system by using the spray condenser, which was developed from previous work. Napier grasses (NG), sugarcane leaves (SL) and rubber leaves (RL) were used as raw material in order to produce as bio-oil. The direct contact heat exchanger called conventional condenser and indirect contact heat exchanger called spray condenser were employed while the bio-oil and the ethanol were also applied as absorber in the spray condenser. The circulating fluidized bed reactor was employed to produce the bio-oil by using fast pyrolysis process. The condition generating the highest yield of the bio-oil production whether the conventional condenser or the spray condenser was 60 kg/hr of feed rate and 480°C of bed temperature. From the result of the bio-oil production, it was found that the highest yields of bio-oil production from NG, SL and RL using conventional condenser were 43.73 %wt, 49.47 %wt and 37.00 %wt, respectively. The highest yield of bio-oil production from NG, SL and RL performing on spray condenser and the using of ethanol as absorber were 55.67 %wt, 62.53 %wt and 44.60 %wt, respectively while the highest yield of bio-oil production from RL performing on spray condenser and the using of bio-oil as absorber was 44.60 %wt. The using of the spray condenser and using of the ethanol as absorber can improve the properties of bio-oil such as heating value and can also increase yield of bio-oil, but the viscosity of bio-oil was increased. Besides, the using of spray condenser can increase the efficiency of energy conversion and can decrease the cost production of bio-oil production, it can also solve the problem about the dirty from the volatile or droplet in the bio-oil that was adhesive in the recirculating blower in case of the system using returned NGC to bio-oil production process.


Author(s):  
Vivek M. Rao ◽  
Marc-Olivier G. Delchini ◽  
Prashant K. Jain ◽  
Mohammad T. Bani Ahmad

Abstract The Oak Ridge National Laboratory (ORNL), in collaboration with Eaton Corporation, has performed computational research and development to design an innovative, direct-contact heat exchanger (DCHE) that is optimized for a low-temperature organic Rankine cycle. A computational fluid dynamics (CFD) model of DCHE was developed in STAR-CCM+ which was later calibrated and validated against the experimental data from literature. The validated CFD model was used to develop an industry-relevant liquid-liquid direct-contact heat exchanger system with water and pentane working fluids. This work heavily relied on high-performance computing (HPC) resources to investigate multiple designs and to identify a baseline design. The innovative design consists of two chambers connected by a converging-diverging nozzle. Phase change for pentane, from liquid to vapor, occurs in the first chamber, whereas the second chamber serves as a separator. Outlets in the second chamber are staggered to prevent entrainment of the liquid water by the gaseous pentane. CFD results confirm that the design behaves as expected and the addition of baffles enhances mixing and heat transfer for higher flow rates while preventing entrainment of gaseous pentane by the liquid water.


2020 ◽  
Vol 42 (1) ◽  
pp. 77-85
Author(s):  
O.I. Sigal ◽  
D.Yu. Paderno

Experimental researches of operational characteristics of laboratory samples of two types of packing for the direct contact heat exchanger have been carried out, - Raschig ceramic rings and the developed construction with using the ribbon of amorphous metal alloy. The metal alloy packing slightly surpasses the ceramic one by the basic operational heat engineering parameters, and contributes to oxidation of the NO to water-soluble NO2, which enables to remove more of the latter by absorption with water and, as a result, to reduce the emissions of nitrogen oxides to the environment after contact apparatus by 35 % more efficiently than with using the ceramic packing.


Author(s):  
Qingtai Xiao ◽  
Wen Luo ◽  
Junwei Huang ◽  
Jianxin Xu ◽  
Hua Wang

By bringing two immiscible fluids at different temperatures into a direct contact heat exchanger (DCHE), bubble swarms are produced in the dual-loop ORC direct contact boiling heat transfer process. The aim of this paper is to make effort to explore the interplay between mixing state quality and heat transfer performance of fluids in the DCHE. Through flow visualization of this mixing process, a simple image analysis technique is introduced to represent the formation and evolution of vapor around the injected coolant droplets. Description of the boiling heat transfer process is here achieved by average volumetric heat transfer coefficient (VHTC). Experimental results attest that the proposed mixing index is powerful and sufficient compared with the Betti numbers method for the mixing quality quantification of bubbles inside DCHE. The synergistic association between the fluids mixing process and the heat transfer process is investigated by statistical regression model of new mixing index and VHTC. The contributions, including the data from monitoring practice in ORC heat transfer system and the proposed way, are presented to delve into the transient behaviors comparison of various fluids mixing and heat transfer processes conveniently.


2020 ◽  
Vol 3 (1) ◽  
pp. 5-19
Author(s):  
Chaerul Qalbi Am

A brief overview and comparison of methods to utilize the Natural Gas Combustion Flue stream. An increase in natural gas usage as fuel and its unique combustion characteristics call for specific waste heat optimization methods. Successful natural gas combustion flue waste heat utilization methods exhibit certain phenomenons. From the overview, it is also discovered that the common waste heat method can be applied to natural gas combustion flue, although the specific condition is required. This paper divides the methods into three categories, non-contact heat exchanger, direct-contact heat exchanger, and thermoelectric generations. Discussions on the result and what affects it are present as well as further studies that can be conducted to expand our scope of knowledge of the subject.


Author(s):  
Johannes Hertel ◽  
Miriam Ebert ◽  
Lars Amsbeck ◽  
Birgit Gobereit ◽  
Jens Rheinländer ◽  
...  

Abstract A direct absorption receiver using ceramic particles (CentRec) has been successfully developed by DLR and tested under solar conditions at the Juelich Solar Power Tower, demonstrating receiver outlet temperatures of more than 900 °C. The next step towards commercial application of the technology is to demonstrate a cost-effective, high temperature heat extraction and transfer to a process medium. Besides e.g. steam for electricity generation in a steam turbine, hot air can be used to supply heat to industrial processes with energy demand at high temperature level. A great potential for higher efficiencies and lower costs has been identified for a moving bed heat exchanger. Several concepts of direct contact heat exchangers have been analyzed and evaluated. The selected concept is a combination of several crossflow-sections that are arranged in series with fluid-mixing-chambers between each crossflow-section. Based on the selected design a heat exchanger prototype with 10 kW thermal power and a design air outlet temperature of 750 °C has been built and integrated into a test setup. The test setup provides particles at 900 °C that are heated up electrically inside a hopper on top of the heat exchanger. Hot particles are then moving downwards (moving bed) from the hopper through the direct contact heat exchanger driven by gravity. Cold air supplied by a compressor flows through the particle bed in cross-flow and is heated up. The hot air flow leaves the heat exchanger with a temperature of 750 °C. The particle mass flow is controlled by an oscillating mass flow controller, positioned under the heat exchanger. The cold particles are collected in a container on the bottom. The particle cycle is closed by transporting them back to the hopper. A measurement and control system is implemented to carry out the tests. The test setup has undergone successful commissioning in October and an extensive testing phase started in January 2019. This paper presents the development and manufacturing as well as the successful commissioning of the heat exchanger prototype.


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