Determining the impact of air-side cleaning for heat exchangers in ventilation systems

2019 ◽  
Vol 41 (1) ◽  
pp. 46-59 ◽  
Author(s):  
Akram Abdul Hamid ◽  
Dennis Johansson ◽  
Michael Lempart
Keyword(s):  
Pressure Drop ◽  
Energy Loss ◽  
Heat Exchangers ◽  
Heat Recovery ◽  
Energy Use ◽  
Ventilation System ◽  
Field Measurements ◽  
The Impact ◽  
Over Time ◽  
Ventilation Systems

Cleaning coils can be an efficient way to reduce the need for reparations and maintain the functionality of a ventilation system. This study builds upon existing knowledge concerning the contamination of heat exchangers. Through field measurements on coils and heat-recovery units, a laboratory experiment on a coil, and a generic calculation example, this study determines the impact of sustained contamination on heat-recovery units with regards to energy use. Field measurements made before and after cleaning of heat exchangers show an average increase in the pressure drop by 12% and decrease in the thermal exchange efficiency by 8.1% due to mass deposited on the surface of the heat exchangers. Results from a laboratory test show a correlation between the mass deposited on a coil and (1) the increase in pressure drop over the coil, as well as (2) a diminishing heat exchange. Accumulating contamination on heat-recovery units in residential and commercial buildings (over time) is then linked to increasing pressure drop and diminishing thermal efficiency. With models based on these links, energy loss over time is calculated based on a generic calculation example in a realistic scenario. Practical application: The results from this study emphasize the need for maintenance of buildings with ventilation systems with coils, but more so those with heat-recovery units. The presented field measurements and laboratory study correlate energy loss with sustained accumulation of contaminants on coils and heat-recovery units. These results should serve as a recommendation to property owners considering maintenance of such units in their buildings.

Numerical Investigation of a Friction Ventilator for Different Geometrical Setups

2016 ◽  
Vol 19 ◽  
pp. 35-42 ◽  
Author(s):  
Julian Praß ◽  
Andreas Renz ◽  
Johannes Weber ◽  
Stefan Becker ◽  
Jörg Franke
Keyword(s):  
Heat Exchangers ◽  
Heat Recovery ◽  
Ventilation System ◽  
Pressure Jump ◽  
Noise Generation ◽  
Temperature Level ◽  
Pressure Losses ◽  
Higher Temperature ◽  
Lower Temperature ◽  
Novel Concept

Conventional ventilation systems with heat recovery used for building aeration exhibit characteristic disadvantages arising from their operating principle such as noise generation from bladed ventilators or remarkable pressure losses generated by heat exchangers. A novel concept that combines ventilators and heat exchanger in one compact friction ventilator that rotates in two separated ducts producing two opposed airflows and transferring thermal energy from the higher temperature airflow to the lower temperature level can overcome the mentioned shortcomings. In order to demonstrate the feasibility of a friction ventilator to operate as ventilation system with heat recovery computational fluid dynamics were used to analyze the resulting pressure jump and volume flow for different geometrical setups. An extensive grid dependency study for a defined operating point that represents the typical use has been carried out in order to improve the numerical results. Furthermore, the results were compared to experimental data whenever possible.

The Use of Decentralized Ventilation Systems with Heat Recovery in the Historical Buildings of St. Petersburg

2014 ◽  
Vol 635-637 ◽  
pp. 370-376 ◽  
Author(s):  
Vera Murgul ◽  
Dusan Vuksanovic ◽  
Nikolay Vatin ◽  
Viktor Pukhkal
Keyword(s):  
Heat Recovery ◽  
Ventilation System ◽  
Energy Performance ◽  
Saint Petersburg ◽  
Exhaust Ventilation ◽  
Different Types ◽  
Energy Efficiency Standards ◽  
Energy Efficient Building ◽  
Cultural Monuments ◽  
Ventilation Systems

Historic apartment buildings in Saint-Petersburg no longer meet today’s energy efficiency standards and need upgrading to achieve lower energy-consumption. The possibilities to upgrade old buildings – historic and cultural monuments – are initially limited. A controlled heat recovery ventilation system is considered to be an integral part of energy efficient building. Provided engineering facilities of a building are updated and reequipped energy performance increases without any impact on building exteriors. Different types of decentralized intake and exhaust ventilation systems with heat recovery based on various types of heat exchangers are considered in a detailed way.

NUMERICAL SIMULATION AND PARAMETRIC STUDIES FOR EVALUATION OF BALANCED VENTILATION AND EARTH AIR EXCHANGERS SYSTEM COUPLED TO A DOMESTIC BUILDING

2013 ◽  
Vol 21 (01) ◽  
pp. 1350002 ◽  
Author(s):  
YOUNES KARTACHI ◽  
ABDELLAH MECHAQRANE
Keyword(s):  
Heat Exchanger ◽  
Heat Recovery ◽  
High Efficiency ◽  
Residential Buildings ◽  
Ventilation System ◽  
Primary Energy ◽  
Climatic Conditions ◽  
Design Parameters ◽  
Climate Data ◽  
The Impact

In this study, we analyze the impact of ventilation heat recovery with the heating and cooling potential of earth air heat exchanger in real climatic conditions in domestic buildings in the Middle Atlas region. In our case study, we calculate the primary energy used by a domestic building built as per the conventional house design parameters required by the Moroccan regulation. We use climate data for the city of Fes in Northern Moroccan. Three system configurations were considered. The first was the mechanical extract ventilation system both with and without heat recovery. The second was the mechanical extract ventilation system with earth to air heat exchanger system (EAHEX), and the third system was the mechanical balanced ventilation system coupled with EAHEX system. Primary energy use strongly influences natural resources efficiency and the environmental impacts of energy supply activities. In this study we explore the primary energy implications of the mechanical balanced ventilation system coupled with the EAHEX system in residential buildings. The results of this study shows that the use of a balanced ventilation system, with a high efficiency instead of a mechanical extract ventilation system, decreases the final and primary energy consumption. Moreover, it decreases or increases the CO2 emission depending on the primary energy sources.

scholarly journals Exergy-based Control of a Dwelling Ventilation System with Heat Recovery

2019 ◽  
pp. 114-116
Author(s):  
Volodymyr Voloshchuk ◽  
Mariya Polishchuk
Keyword(s):  
Power Consumption ◽  
Heat Recovery ◽  
Operation Mode ◽  
Ventilation System ◽  
Primary Energy ◽  
Energy Sources ◽  
Annual Saving ◽  
Operating Modes ◽  
Ventilation Systems

On the base of exergy-based approach it is shownthat for the ventilation systems there are operating modes forwhich heat recovery increases exergy of fuel expended to providethe ventilation air compared to cases without bringing anyrecovery of heat and additional power consumption to drive theair flow by the fans. For the specified system, in case of switchingventilation unit to the operation mode of lower values of spentfuel exergy it is possible to provide annual saving from 5 to 15 %of the primary energy sources.

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.

scholarly journals Performance assessment of demand controlled ventilation controls concerning indoor VOC exposure based on a dynamic VOC emission model

2019 ◽  
Vol 111 ◽  
pp. 01051
Author(s):  
Klaas De Jonge ◽  
Arnold Janssens ◽  
Jelle Laverge
Keyword(s):  
Performance Assessment ◽  
Building Materials ◽  
Ventilation System ◽  
System Level ◽  
System Control ◽  
Emission Model ◽  
Controlled Ventilation ◽  
Demand Controlled Ventilation ◽  
The Impact ◽  
Ventilation Systems

The performance assessment of ventilation systems often focusses only on CO2 and humidity levels. The indoor Volatile Organic Compounds (VOC) emissions of building materials or other products is thereby overlooked. The new generation of ventilation systems, Demand Controlled Ventilation (DCV), are systems that do not supply the nominal airflow continuously but are controlled by CO2 or humidity sensors in order to save energy. This poses potential problems for exposure to VOCs. In this study, a dynamic VOC model, which takes into account changing temperature and humidity that was derived from literature, is implemented in a CONTAM model of the Belgian reference apartment. The impact of a DCV system on the indoor VOC levels is investigated. Results show that the use of a dynamic model is necessary compared to the previously used approximation of a constant emission. Furthermore, on a system level, the influence of the ventilation system control on the indoor VOC levels shows. The overall VOC concentration in the different rooms will be higher because of lowered ventilation rates. Especially in rooms that are often unoccupied during the day, the accumulation of VOCs shows. In the development of DCV system controls, the aspect of VOC exposure should not be overlooked to be able to benefit from both the energy savings and improved Indoor Air Quality (IAQ).

scholarly journals Performance of Supercritical CO2 Power Cycle and Its Turbomachinery with the Printed Circuit Heat Exchanger with Straight and Zigzag Channels

Energies ◽  
2020 ◽  
Vol 14 (1) ◽  
pp. 62
Author(s):  
Muhammed Saeed ◽  
Khaled Alawadi ◽  
Sung Chul Kim
Keyword(s):  
Reynolds Number ◽  
Heat Exchanger ◽  
Pressure Drop ◽  
Heat Exchangers ◽  
Straight Channel ◽  
Printed Circuit ◽  
Cycle Simulation ◽  
Overall Performance ◽  
Channel Configuration ◽  
The Impact

Since printed circuit heat exchangers (PCHE) are the largest modules of a supercritical carbon dioxide Brayton cycle, they can considerably affect the whole system’s performance and layout. Straight-channel and zigzag-channel printed circuit heat exchangers have frequently been analyzed in the standalone mode and repeatedly proposed for sCO2−BC. However, the impact of heat exchanger designs with straight and zigzag-channel configurations on the performance of the cycle and its components, i.e., the turbine and compressor, has not been studied. In this context, this study evaluates the effect of different heat exchanger designs with various values of effectiveness (ϵ), inlet Reynolds number (Re), and channel configuration (zigzag and straight channel) on the overall performance of the sCO2−BC and its components. For the design and analysis of PCHEs, an in-house PCHE design and analysis code (PCHE-DAC) was developed in the MATLAB environment. The sCO2−BC performance was evaluated utilizing an in-house cycle simulation and analysis code (CSAC) that employs the heat exchanger design code as a subroutine. The results suggest that pressure drop in PCHEs with straight-channel configuration is up to 3.0 times larger than in PCHEs with zigzag-channel configuration. It was found that a higher pressure drop in the PCHEs with straight channels can be attributed to substantially longer channel lengths required for these designs (up to 4.1 times than zigzag-channels) based on the poor heat transfer characteristics associated with these channel geometries. Thus, cycle layouts using PCHEs with a straight-channel configuration impart a much higher load (up to 1.13 times) on the recompression compressor, this in turn, results in a lower pressure ratio across the turbine. Therefore, the overall performance of the sCO2−BC using PCHEs with straight-channel configurations is found to be substantially inferior to that of layouts using PCHEs with zigzag-channel configurations. Finally, optimization results suggest that heat exchanger’s design with inlet Reynolds number and heat exchanger effectiveness ranging from 32 k to 42 k and 0.94>ϵ>0.87, respectively, are optimal for sCO2−BC and present a good bargain between cycle efficiency and its layout size.

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