scholarly journals Effect of Supply and Exhaust Air Velocity on the Enthalpy and Temperature Exchange Efficiency of a Paper Heat Exchanger

2021 ◽  
Vol 335 ◽  
pp. 03006
Author(s):  
Hong Jian Hua ◽  
Abudulkareem Sh. Mahdi Al-Obaidi ◽  
Chin Wai Meng ◽  
Kenny James Ling Neng Hui
Keyword(s):  
Heat Exchanger ◽  
Indoor Air ◽  
Heat Exchangers ◽  
Heat Recovery ◽  
Dust Particles ◽  
Data Logger ◽  
Air Velocity ◽  
Air Inlet ◽  
Fan Speed ◽  
Temperature Exchange

Heat Recovery Ventilators (HRV) are gradually becoming more popular in urban cities and buildings as it is able to effectively maintain the indoor air quality while also using minimal amounts of energy. The key component in the HRV is the Paper Heat Exchanger, which allows the heat exchange of indoor and outdoor air through a crossflow, while also filtering out stale air and dust particles. This article investigates the effect of manipulating the supply and exhaust air velocity on the enthalpy and temperature exchange efficiency of a paper heat exchanger. Data is obtained from experimental results, where the experiments are conducted in a test lab using heat recovery ventilators (HRV) installed with paper heat exchangers. Two paper heat exchangers from different suppliers were tested inside a HRV installed in an air conditioned room. The HRV fan speed was varied at a fixed interval of 0.5 m/s, and the air velocity was measured by using a wind speed meter. At the same time, a USB data logger was used to collect relative humidity and temperature of the air at the supply inlet, indoor air inlet, and return air outlet to determine temperature exchange efficiency and the enthalpy of air. The results of the testing shows that the HRV was able to achieve a temperature exchange efficiency of 47 to 63% and enthalpy exchange efficiency of 63 to 94% for PHEX-A, and a temperature exchange efficiency of 28 to 48% and enthalpy exchange efficiency of 57 to 85% for PHEX-B. The data shows that PHEX-A has higher efficiency than PHEX-B.

Modeling Large-Size Boilers As a Set of Heat Exchangers: Tips and Tricks

2001 ◽  
Author(s):  
Cristóbal Cortés ◽  
Luis I. Díez ◽  
Antonio Campo
Keyword(s):  
Heat Exchanger ◽  
Heat Exchangers ◽  
Heat Recovery ◽  
Practical Calculation ◽  
Approximate Methods ◽  
Monitoring Method ◽  
Large Size ◽  
Thermoelectric Plant ◽  
The One

Abstract Practical calculation of the heat-recovery sections of large-size boilers is still based on approximate methods. On the one hand, CFD-based models cannot directly handle the geometric intricacy of tube bundles, and thus rely on volume-averaged source terms that demand empirical input. On the other hand, the standard, lumped heat exchanger calculation, which can be a far simpler and more robust alternative, fails in several important aspects, mainly related to the effects of thermal radiation and the coupling between several sections. In this paper, we consider the diverse sections of a coal-fired utility boiler as a case study to show how to deal with these shortcomings. Under the objective of developing a simple monitoring method, we extend the traditional heat exchanger model to take into account most of the peculiarities of boiler superheaters, reheaters and economizers. Techniques range from the re-examination of analytical solutions to the auxiliary use of CFD calculations. The models are assembled to simulate the thermal performance of the boiler as a whole unit. Results are validated against actual measurements taken at a thermoelectric plant.

The Potential Danger of Fire in Gas Turbine Heat Exchangers

1969 ◽  
Author(s):  
C. F. McDonald
Keyword(s):  
Heat Exchanger ◽  
Gas Turbine ◽  
Heat Exchangers ◽  
Heat Recovery ◽  
Waste Heat Recovery ◽  
Waste Heat ◽  
Engine Operation ◽  
Exhaust Heat ◽  
The Subject ◽  
Gas Turbine Cycle

Increased emphasis is being placed on the regenerative gas turbine cycle, and the utilization of waste heat recovery systems, for improved thermal efficiency. For such systems there are modes of engine operation, where it is possible for a metal fire to occur in the exhaust heat exchanger. This paper is intended as an introduction to the subject, more from an engineering, than metallurgical standpoint, and includes a description of a series of simple tests to acquire an understanding of the problem for a particular application. Some engine operational procedures, and design features, aimed at minimizing the costly and dangerous occurrence of gas turbine heat exchanger fires, are briefly mentioned.

Modelling the Transient Behaviour of Heat Recovery Steam Generators

1995 ◽  
Vol 209 (4) ◽  
pp. 265-273 ◽  
Author(s):  
P J Dechamps
Keyword(s):  
Heat Exchanger ◽  
Heat Exchangers ◽  
Heat Recovery ◽  
Computation Time ◽  
Assisted Circulation ◽  
Steam Generators ◽  
Two Phase ◽  
Linear Heat ◽  
Numerical Predictions ◽  
Equivalent Linear

This paper describes a method used to compute the transient performances of assisted circulation heat recovery steam generators. These heat recovery steam generators are composed of several heat exchangers, each of which is a bundle of tubes. The method presented here treats each heat exchanger in a similar way, replacing the bundle of tubes with an ‘equivalent’ linear heat exchanger. This equivalent linear heat exchanger is then discretized in as many slices as required by the accuracy. The mass and enthalpy equations on each of these control volumes are solved by a fully explicit numerical method, adapted for the special conditions encountered in this kind of problem, allowing a considerable reduction of the computation time compared to other methods. Some emphasis is put on the modifications required to solve the equations for the evaporators because they are two-phase heat exchangers. A model for the steam drums is also presented together with simple models for the main control loops used in such systems. An example is presented in which an existing dual pressure level heat recovery steam generator is started from a cold state. The numerical predictions are in good agreement with measurements.

scholarly journals Numerical and Experimental Study of the Thermal Efficiency of an Air-Soil Heat Exchanger in the Sahelian Zone

2021 ◽  
pp. 8-16
Author(s):  
Boureima Kaboré ◽  
Germain Wende Pouiré Ouedraogo ◽  
Adama Ouedraogo ◽  
Sié Kam ◽  
Dieudonné Joseph Bathiebo
Keyword(s):  
Experimental Study ◽  
Heat Exchanger ◽  
Thermal Efficiency ◽  
Heat Exchangers ◽  
Air Conditioning ◽  
Electrical Energy ◽  
Tube Length ◽  
Air Velocity ◽  
June July ◽  
Sahelian Zone

In the Sahelian zone, air conditioning in house by air-soil heat exchangers is an alternative in the context of insufficient of electrical energy. In this work, we carried out a numerical and experimental study of thermal efficiency of an air-soil heat exchanger. This study provided an estimation of thermal efficiency of an experimental air-soil heat exchanger during June, July and August 2016. Numerical results provided a better understanding of the influence of parameters such as tube length, air velocity and soil temperature on the thermal efficiency of this system.

scholarly journals The influence of airflow on the effectiveness of rotary heat exchangers operating under high-speed rotor conditions

2019 ◽  
Vol 116 ◽  
pp. 00032
Author(s):  
Paulina Kanaś ◽  
Andrzej Jedlikowski ◽  
Sergey Anisimov ◽  
Borys Vager
Keyword(s):  
Mass Transfer ◽  
Heat Exchanger ◽  
Heat And Mass Transfer ◽  
Heat Exchangers ◽  
Heat Recovery ◽  
High Speed ◽  
Airflow Rate ◽  
Sharp Drop ◽  
Transfer Processes ◽  
Mass Transfer Processes

The paper presents an analysis of heat and mass transfer processes occurring inside the rotary heat exchanger operating under high-speed rotor conditions for different values of the airflow rate. For this purpose the original mathematical α-model was used. Conducted computer simulations allowed to determine the influence of Number of Transfer Units (NTU) of airflow on the temperature effectiveness as well as on the distribution of different active heat and mass transfer zones: “dry”, “wet” and “frost”. It was found that the increase of the values of NTU strictly affects the increase of the effectiveness of heat recovery. Another issue emerging from this study is the fact that in the certain range of low values of NTU there is no “dry” area created. It was established that at low values of NTU (NTU≈1) “frost” area extremum and sharp drop in the “frost” area accumulation are observed.

scholarly journals Investigation on the Optimum Design of Heat Exchangers in a Hybrid Closed Circuit Cooling Tower

1970 ◽  
Vol 37 ◽  
pp. 52-57
Author(s):  
MMA Sarker
Keyword(s):  
Heat Exchanger ◽  
Optimum Design ◽  
Heat Exchangers ◽  
Cooling Tower ◽  
Cooling Capacity ◽  
Closed Circuit ◽  
Design Parameters ◽  
Air Inlet ◽  
Staggered Arrangement ◽  
Temperature And Pressure

Investigation on the optimum design of a heat exchanger in a Hybrid Closed Circuit Cooling Tower having a rated capacity of 1RT is performed experimentally. The heat exchanger of dimension 0.4mx0.33mx0.572m has 15x7 bare type 15.88mm OD copper coils in staggered arrangement. The relevant design parameters were selected based on the typical East Asian meteorological constrains for the year-round smooth operation of the cooling tower. This study presents results related to the cooling capacity and the cooling efficiency with respect to wet bulb temperature and pressure drop with respect to air inlet velocity. Results are also presented in terms of number of transfer units (NTU). Cooling capacity was found to be close to the rated one for the wet mode but low in dry mode operation. Keywords: Hybrid closed circuit cooling tower, Cooling capacity, Wet mode, Dry modedoi:10.3329/jme.v37i0.820Journal of Mechanical Engineering Vol.37 June 2007, pp.52-77

scholarly journals The Effect of Supply and Outdoor Air Temperature on The Enthalpy and Temperature Exchange Efficiency of a Paper Heat Exchanger

2021 ◽  
Vol 335 ◽  
pp. 03015
Author(s):  
Teoh Zhi Heng ◽  
Abudulkareem Sh. Mahdi Al-Obaidi ◽  
Chin Wai Meng ◽  
Kenny James Ling Neng Hui
Keyword(s):  
Heat Exchanger ◽  
Air Temperature ◽  
Indoor Air ◽  
Numerical Models ◽  
Outdoor Air ◽  
Iso Standard ◽  
Air Temperatures ◽  
Temperature Exchange ◽  
Main Component ◽  
Complex Cases

Heat Recovery Ventilator (VHR) is widely used nowadays as it is capable to maintain high Indoor Air Quality (IAQ) while minimizing the energy loss of indoor air through air-to-air heat exchanger principle. The main component that enables VHR to perform air-to-air heat exchange is known as Paper Heat Exchanger (PP-HEX). Hence, the objective of this research is to study and analyse the performance of a PP-HEX under different return and outdoor air temperatures as well as their effect on both enthalpy and temperature exchange efficiency. Moreover, some numerical models of VHR have been developed to optimize some complex cases and the numerical models are meant to reduce the physical experiments to analyze or improve complex cases in the future. To the best of the authors knowledge, there is no experimental data available from any sources to validate the numerical models. To address this issue, two different supplies of PP-HEX are tested with an actual VHR, and both PP-HEXs will be referred to as PP-HEX-A and PP-HEX-B due to confidentiality. Furthermore, the testing is conducted in a temperature-controlled testing laboratory and the testing conditions are set according to the ISO standard. The preliminary testing results show that the temperature exchange efficiency and enthalpy exchange efficiency of the PP-HEXs have the same trends while the outdoor air temperature is fixed and varying the temperature of indoor air. In contrary, the temperature exchange efficiency and enthalpy exchange efficiency of the PP-HEXs have the same trends while the indoor air temperature is fixed and varying the temperature of outdoor air as well. With the default voltage supplies (240V) to VHR and the setup conditions (according to the ISO Standard) of return air to be 27°C and outdoor air to be 35°C, the testing results show that PP-HEX-A has a temperature exchange efficiency and enthalpy exchange efficiency with a range of (37.97 – 40.28) % and (30.77 – 57.81) % respectively. While PP-HEX-B has a temperature exchange efficiency and enthalpy exchange efficiency with a range of (35.29 – 42.5) % and (39.6 – 55.93) % respectively.

scholarly journals Minimization of the Lifecycle Cost of a Rotary Heat Exchanger Used in Building Ventilation Systems in Cold Climates

2021 ◽  
Vol 67 (6) ◽  
pp. 302-310
Author(s):  
Ignas Sokolnikas ◽  
Kęstutis Čiuprinskas ◽  
Jolanta Čiuprinskienė
Keyword(s):  
Heat Exchanger ◽  
Heat Exchangers ◽  
Heat Recovery ◽  
Foil Thickness ◽  
Geometrical Parameters ◽  
Cold Climates ◽  
Heat Transfer Efficiency ◽  
Air Handling Unit ◽  
Building Ventilation ◽  
Ventilation Systems

This article presents an analysis of rotary heat exchangers (RHE) used as heat recovery units in building ventilation systems in cold climates. Usually, heat exchangers with the highest heat transfer efficiency are the preferable option for this purpose. However, such exchangers usually have the highest media pressure drop, thus requiring the highest amount of energy for media transportation. In this study, the problem is solved by analysing the lifecycle cost (LCC) of the RHE including both the recovered heat and the electricity consumed in the fans of the air handling unit (AHU). The purpose of the investigation was to determine the optimal set of geometrical characteristics such as the exchanger’s length, foil thickness, the height and width of the air channel. Two hundred and seventy different combinations were examined using analytical dependencies and ANSYS simulations. The results are compared with experimental data obtained earlier at the KOMFOVENT laboratory. The results show that the best overall energy efficiency is obtained in heat exchangers that do not offer the best heat recovery efficiency, and LCC differences in the same climatic and economic conditions can go as high as 31 %, mainly due to the geometrical parameters of the heat exchanger.

Thermal-Hydraulic Behavior and Prediction of Heat Exchanger for Latent Heat Recovery of Exhaust Flue Gas

1999 ◽  
Author(s):  
Masahiro Osakabe
Keyword(s):  
Heat Exchanger ◽  
Latent Heat ◽  
Flow Rate ◽  
Flue Gas ◽  
Heat Exchangers ◽  
Pressure Loss ◽  
Heat Recovery ◽  
Finned Tubes ◽  
Temperature Distributions ◽  
Inner Diameter

Abstract In order to improve the boiler efficiency, latent heat recovery from the flue gas is very important concept. Three kinds of countercurrent cross-flow heat exchangers, which consist of bare tubes, spirally finned tubes of fin pitch 5 and 10mm, were designed and used for the experiment. The heat exchanger of the bare tubes consists of a staggered bank of 5-4 rows and 50 stages. The length, outer and inner diameter of the bare tube is 482, 27.2 and 23.2mm, respectively. The heat exchangers of finned tubes consist of staggered banks of 3-2 rows, 34 stages for the fin pitch 10mm and 20 stages for the pitch 5mm. The length, outer and inner diameter of the base tube welded with the fins is 482, 34 and 28.8mm, respectively. The thickness and height of the plate fin are 1 and 12mm, respectively. The parametric study varying the flue gas flow rate, feed water temperature and flow rate was conducted. The temperature distributions of water and flue gas in the heat exchanger were measured with sheath K-type thermocouples of 1.6 mm in diameter. The pressure loss and the total amount of condensate generated in the heat exchanger were also measured. Based on the previous basic studies, a prediction method for the heat exchanger was proposed. In the prediction, the flue gas was treated as a mixture of CO2, CO, O2, N2 and H2O, and the one-dimensional heat and mass balance calculation along the flow direction of flue gas was conducted. The heat and mass transfer on tubes was evaluated with a simple analogy correlation. For the finned tubes, the fin efficiency at the condensing region was calculated with a semi-empirical correlation obtained in the previous basic study. The effect of condensate film on the tubes was considered to be negligibly small for the heat transfer and pressure loss calculation. The experimental results for the temperature distributions of water and flue gas in the test heat exchangers with bare and finned tubes agreed well with the prediction.

COMPARISON OF HEAT EXCHANGER DESIGNS FOR SHIP BALLAST WATER HEAT TREATMENT SYSTEM

2015 ◽  
Vol 77 (8) ◽  
Author(s):  
Rajoo Balaji ◽  
Omar Yaakob ◽  
Kho King Koh ◽  
Faizul Amri Adnan ◽  
Nasrudin Ismail ◽  
...  
Keyword(s):  
Heat Exchanger ◽  
Ballast Water ◽  
Heat Exchangers ◽  
Heat Recovery ◽  
Waste Heat Recovery ◽  
Waste Heat ◽  
Treatment System ◽  
Heat Exchanger Design ◽  
Good Resource ◽  
Ship Ballast Water

Sterilisation by heat can be a capital treatment for ballast water and waste heat from ship’s engines will be a good resource. Based on the waste heat availability on an operational tanker, a ballast water treatment system was envisaged including a shipboard heat exchanger for waste heat recovery. To verify the heat availability and the species’ mortalities, test rigs were arranged similar to shipboard arrangement. For assessing the smaller heat exchangers for the tests, designs were developed using Bell-Delaware approaches based on the shipboard heat exchanger design. The thermodynamic and geometric values were computed and the features of the commercially available and fitted heat exchangers were compared with the developed designs. Two commercially procured heat exchangers fitted on two separate engine test rigs were used for tests. The designs of commercially procured heat exchangers were close to the developed designs and were found to be suitable for the tests planned.

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