Double Heat Exchanger Research Articles

Design and Performance Analysis of a Small-Scale Prototype Water Condensing System for Biomass Combustion Flue Gas Abatement

This article outlines the design and performance of a flue gas condensation system integrated with a biomass combustion plant. The system comprises a biomass plant fuelled by wood chips, generating flue gases. These gases are condensed via a double heat exchanger set-up, extracting water and heat to reduce concentrations of CO, CO2, and NOx while releasing gases at a temperature close to ambient temperature. The 100 kW biomass plant operates steadily, consuming 50 kg of wood chips per hour with fuel energy of 18.98 MJ/kg. Post combustion, the gases exit at 430 °C and undergo two-stage cooling. In the first stage, gases are cooled in a high-temperature tube heat exchanger, transferring heat to air. They then enter the second stage, a flue gas/water heat exchanger, recovering sensible and latent thermal energy, which leads to water condensation. Flue gas is discharged at approximately 33 °C. Throughout, parameters like the flue gas temperatures, mass flow, fuel consumption, heat carrier temperatures, and water condensation rates were monitored. The test results show that the system can condense water from flue gas at 75 g/min at 22 °C while reducing pollutant emissions by approximately 20% for CO2, 19% for CO, 30% for NO, and 26% for NOx.

Advances in triple tube heat exchangers regarding heat transfer characteristics of single and two-phase flows in comparison to double tube heat exchangers part 1

Abstract Triple concentric-tube heat exchangers are used widely in refrigeration, drying, energy storage, chemical systems, and the food industry. To handle excessive temperature differences, the heat transfer area, as an option, the heat exchanger’s length, is necessary to be increased. Triple tubes have a significant advantage in this regard in comparison to double ones. The target of this review is to discuss the most recent publications, including the single-phase flows in these heat exchangers, focusing on the heat transfer and hydrodynamic characteristics, and to classify them with various contemporary aspects. The operating conditions, enhanced surfaces, and sizes, as well as the geometrical parameters, are categorized as being part of experimental, numerical, and analytical research. The studies indicate that the heat transfer characteristics of triple concentric-tube heat exchangers are better than those of double tube heat exchangers. In single-phase studies, the convective and overall heat transfer coefficients, Nusselt number, heat transfer rate, and effectiveness are greater in triple heat exchangers than in double heat exchangers, and the heat exchanger length required to achieve the same heat transfer performance is shorter in triple heat exchangers than in double heat exchangers. Heat transfer surface area increases by adding a concentric third tube. Advanced surfaces enhance heat transfer compared to smooth surfaces and flow turbulence in comparison to smooth surfaces. Heat transfer from triple-one enhanced surfaces is not well-analyzed. Design and use of triple ones as a double one’s alternative should advance shortly.

Advanced solutions to improve heat recovery from wastewater in a double heat exchanger

Reducing energy consumption and CO2 footprint in existing buildings without requiring extensive construction work is one of the biggest challenges facing the globe today. Although heating contributes for the majority of energy use in buildings, residential hot water demand is also relatively high, particularly when daily usage is high and especially for certain applications. The use of technologies that recover energy from sources other than fossil fuels to heat water has grown crucial, and one such technology involves recovering thermal energy from wastewater. Typically, heat recovery from wastewater is made to collect any remaining energy from the hot drainage water, and this energy is then applied to heat pumps or to warm up incoming cold water. The paper presents numerical simulations using a SST k-ω turbulence model in order to compare a regular geometry of heat exchanger with a helicoidal one. The second one provides a more turbulent flow that allows an intensification of the outer flow, thus allowing the enhancement of the heat transfer from the inner heated flow to the outer flow.

Study of the energy performance of a combined system: Solar thermal collector – Storage tank – Floor heating, for the heating needs of a room in Maghreb climate

This paper presents the study of the energy performance of a solar thermal combined system (STCS) composed of: a solar thermal collector; a storage tank with double heat exchangers and a floor heating system to meet the heating needs of a local taken in the Maghreb climate context. The original idea of this study is the consideration of a storage tank with integrated double exchangers allowing on the one hand the accumulation of heat under the action of the exchanger1 connected to the circuit of the collector, to receive the surplus of solar thermal energy during the day and on the other hand to supply it under the action of the exchanger2 as auxiliary heating in the evening to the heating floor. A numerical model of the STCS system was developed under the TRNSYS simulation program. For the validation of the model of the heating floor coupled with the solar thermal collector (DSF), the results obtained by simulation were compared to those from the experiment conducted on a test cell equipped with a heating floor in the climatic conditions of the city of Oran. Other simulations of the STCS system were performed by integrating the storage tank and considering a function regulation strategy, in two stages of the storage tank, between day and night where the efficiency of the tank as a back-up heater was evaluated. The results obtained by simulation show the reliability of the model and the efficiency of the storage tank used as a back-up heater with a coverage rate of 91%. The combined solar thermal system STCS provides energy savings by substituting electric or gas back-up with active solar storage, under the application of an energy management strategy.

Improving the efficiency of energy recovery from wastewater by using a double heat exchanger to protect the environment

A possible strategy for reducing energy consumption and carbon dioxide emissions in order to protect the environment is the recovery of heat from wastewater. This study aims to achieve an improvement in the effectiveness of heat transfer by changing the flow parameters by using a double heat exchanger to recover the heat from greywater. The results, the thermal energy from wastewater can be recovered, the effectiveness ranged between (25 % — 45 %) with the discharge of (0.15-0.51m3/h) lower to higher, respectively. The cold water flow has a clear effect on the heat transfer efficiency, the decrease in cold water velocity led to the increase in heat transfer performance. This technique is simple to implement and inexpensive. It can be designed and built on the basement of the multi-storey building. The dual heat exchanger splits the flow into two-pipe, decreasing the flow rate velocity and thus, increasing the heat transfer efficiency.

Application of soft computing techniques to optimize thermal parameters in a double heat exchanger with cylindrical turbulators

AbstractIn the present study, the dimensions of the cylindrical turbulators have been optimized to achieve the highest thermal performance. A double pipe heat exchanger with cylindrical turbulators placed in the annulus side is modeled and a numerical simulation is carried out for different operating conditions. The simulation is conducted for different diameters of the turbulators for various Re for the annulus fluid. The Nusselt number (Nu), friction factor (f), and thermohydraulic performance index (THPI) are the responses simulated for the above different cases of input conditions. Response surface methodology has been used to study the influence of operating parameters on the responses. It is observed that Nu, f, and THPI increased as the Re and turbulator diameter increased. Response optimizer is used to optimize the turbulator diameter to obtain the highest thermal performance in terms of highest Nu and THPI and lowest f. The results indicated that maximum performance was obtained for a diameter of 4.45 mm and for a Re of 5530. The Nu and THPI corresponding to the above combinations are 68.4 and 2, respectively.

Experimental investigation of perforated twisted tapes turbulator on thermal performance in double pipe heat exchangers

In this paper, the experimental effect of the continuous and discontinuous twisted tapes turbulator (perforated and non-perforated) on the inner side of the internal tube in the double heat exchangers on heat transfer, the friction coefficient, and thermal performance have been discussed. On discontinuous twisted tapes turbulator, 9 holes with different geometries, such as triangular, square, rectangular, circular, and diamond with the triangular arrangement, have been created on turbulator flat surfaces. The Reynolds range is investigated at 5500–10000, and working fluids are on the side of the inner tube and annular space is hot and cold water, respectively. Experimental results have shown that discontinuous turbulator has a better effect on heat transfer and pressure drop than continuous turbulator. As the discontinuous turbulator without a hole has an increase in heat transfer of 8.2 % and a reduction of 9.8 % in the pressure drop coefficient compared to the continuous turbulator. Then the effect of perforation on discontinuous twisted tapes turbulator was investigated. Experimental results show that perforated discontinuous turbulator with circular, square, rectangular, diamond and triangular perforation with the same hydraulic diameter as for discontinuous turbulator without perforation was 20.8 %, 15 %, 11 %, 8.7 %, 5 % increase in heat transfer and 27.7 %, 22.8 %, 17.3 %, 12.1 %, 5.5 % decrease in the coefficient of pressure drop, respectively. Therefore, according to the results, the best thermal performance was related to the perforated of perforated discontinuous twisted turbulator, discontinuous twisted turbulator, and continuously twisted turbulator were respectively.

Experimental and numerical investigations of thermal performance of Al2O3/water nanofluid for a combi boiler with double heat exchangers

Purpose This study aims to focus on usage of Al2O3/water nanofluid as working fluid in a combi boiler. The plate heat exchanger located at the bottom of the combi boiler has been used for heating the domestic water in the present study. Al2O3/water nanofluid has also been used in obtaining of the heat energy provided from combustion. Therefore, thermal performance of Al2O3/water has been determined by comparing water and nanofluid-water mixture. The present study also investigates heat transfer rates as numerical and experimental for varying cold side outlet temperatures, comparatively. Design/methodology/approach The present study has included both experimental and numerical methodologies. The experimental setup consists of main heat exchanger, atmospheric burner, circulation pump and plate-type heat exchanger in which the Al2O3/water nanofluid was used as working fluid to heat the domestic water. In the numerical part of the study, a commercial computational fluid dynamic code has been used to model heat rate and thermal efficiency of the heat exchanger used. Findings It has been concluded that the predicted results are in satisfactorily good agreement with the measured data. In the experimental part of the study, the flow rate of Al2O3/water nanofluid was kept constant during the experiments. The flow rates of the water by which the heated Al2O3/water nanofluid mixture was cooled via the plate heat exchanger have been changed as 3, 4, 5 and 6 lpm. The domestic water temperatures that were kept constant have also been changed as 40°C, 45°C, 50°C, 55°C and 60°C. It has been concluded that the Al2O3/water nanofluid thermal efficiency has been 16 per cent better than pure water. Originality/value The main originality of the present study is that thermal efficiency of the plate-type heat exchanger when Al2O3/water mixture nanofluids are used as there are limited studies related to the usage of Al2O3/water mixture nanofluids in the plate-type heat exchanger not only experimental but also numerical methodologies.

Design and analysis of double pipe counter flow heat exchanger (condenser) to produce hot water as modification of air conditioner split condenser

This study was conducted to design a heat exchanger double pipe counter flow as a condenser to produce hot water that can be used for various purpose like a warm bath. Hot fluid flows in copper with cold fluid flowing in the annulus. The hot fluid used is R-22 while the cold fluid used is water. This pipe double heat exchanger is measuring 112.04 cm in length by 29 cm in width and 20.3 cm in height. Inside of pipe using copper with diameter ¼ inch. And total length of the copper pipe 18.915 m. While on the annular pipe using PVC pipe with ½ inch size. The total length of the annulus pipe is 16.128 m. In addition, heat exchanger is used to determined heat released by the condenser, coefficient of performance (COP) of vapor compression cycle, efficiency vapor compression cycle and temperature of the condenser-generated hot water.

Determination of the Global Heat Transfer Coefficient of a Double Heat Exchanger Battery in a Dry Mode.

The cold battery is a heat exchanger between two fluids, air (secondary fluid) and iced water (primary fluid). The cold battery is composed of two heat exchangers in series, one of which is made up of flat-plate in galvanized steel serving as a reservoir for the iced water and the other one a copper shell and-tube exchanger with aluminum cooling blades. The two heat exchangers a connected pipe of the same diameter. These pipes will permit the transit of the iced water coming from the flat-plate exchanger by gravitation towards the tubes of the second exchanger. These two heat exchangers are incorporated in a galvanized container coupled with a centrifugal fan for the improvement of the thermal comfort. The water, after passing through the two heat exchangers is stored in an adiabatic reservoir and will serve as a water fountain [1]. The modeling will be done in a humid mode that is the temperature of the surface of the battery is very low compared with the dew temperature of air. The cooling allows the condensation of water vapor [2]. The characterization of that cold battery will be done in a dry regime where there is only one heat exchanger and the quantity of vapor contained in the air does not vary and also the surface temperature of the battery is greater than the dew temperature of air [2; 3].

Charaterization of a cold battery with double heat exchanger in a dry mode

The cold battery is a heat exchanger between two fluids, air (secondary fluid) and iced water (primary fluid). The cold battery is composed of two heat exchangers in series, one of which is made up of flat-plate in galvanized steel serving as a reservoir for the iced water and the other one a copper shelland-tube exchanger with aluminum cooling blades. The two heat exchangers a connected pipe of the same diameter. These pipes will permit the transit of the iced water coming from the flat-plate exchanger by gravitation towards the tubes of the second exchanger. These two heat exchangers are incorporated in a galvanized container coupled with a centrifugal fan for the improvement of the thermal comfort. The water, after passing through the two heat exchangers is stored in an adiabatic reservoir and will serve as a water fountain [1,2]. The characterization of that cold battery will be done in a dry regime where there is only one heat exchanger and the quantity of vapor contained in the air does not varied and also the surface temperature of the battery is greater than the dew temperature of air [3 ; 4; 5].