Experimental Study of Heat Storage Unit Made of PCM-gypsum Composite Integrated with the Ventilation System of the Building

2017 ◽  
Author(s):  
Maciej Jaworski ◽  
Hanna Jędrzejuk ◽  
Rafał Laskowski
Keyword(s):  
Heat Storage ◽  
Air Flow ◽  
Ventilation System ◽  
Ambient Air ◽  
Heat Transfer Process ◽  
Night Time ◽  
Storage Unit ◽  
Regenerative Heat ◽  
Air Temperatures ◽  
Set Up

In the paper a special heat storage unit for building applications is presented. It has a form of a ceiling panel that is made of PCM-gypsum mortar composite and it contains internal channels for air flow, since it is designed as a part of ventilation system of the building. The panel works as a regenerative heat exchanger with phase change material (PCM) as a prevailing heat storage medium. When a melting point of PCM is properly chosen it is possible that air temperature flowing into the building reach a level corresponding to thermal comfort conditions, regardless the temperature at the intake. Warm air (during a day) releases heat basically to PCM causing its melting. During night time cool ambient air is heated up while it takes back heat accumulated in PCM. An experimental set-up based on the above concept was developed. A series of tests in different conditions (for variable inlet air temperatures, air flow rates) were performed. Information on thermal performance of the ceiling panel as well as detailed data on heat transfer process were obtained and discussed in the paper.

scholarly journals Energetic investigation of energy recovery technologies in air handling units

2018 ◽  
Vol 9 (1) ◽  
pp. 49-57
Author(s):  
L. F. Al-Hyari ◽  
M. Kassai
Keyword(s):  
Energy Consumption ◽  
Indoor Air ◽  
Energy Recovery ◽  
Ventilation System ◽  
Ambient Air ◽  
Existing Buildings ◽  
Exact Methods ◽  
Technical Data ◽  
Air Temperatures ◽  
Air Handling Units

The statistical data show that the application of active cooling is spread widely in residential and commercial buildings. In these buildings, the ventilation is significantly increased in the whole energy consumption. There are similar problems in the operation of post-insulation of existing buildings. In this case, the energy consumption of the ventilation system gives a major proportion of the whole building services energy consumption. The opportuneness of this research shows that the actual available calculation procedures and technical designing data are only rough approximations for analyzing the energy consumption of air handling units and the energy saved by the integrated heat or energy recovery units. There are not exact methods and unequivocal technical data. In previous researches, the production and development companies have not investigated the effectiveness of the energy recovery units under difference ambient air conditions and the period of defrost cycle when the heat recovery can only partly operate under difference ambient air temperatures. During this term, a re-heater has to fully heat up the ambient cold air to the temperature of supplied air and generate the required heating demand to provide the necessary indoor air temperature.

scholarly journals Performance of solar dryer chamber used for convective drying of sponge-cotton

2014 ◽  
Vol 18 (suppl.2) ◽  
pp. 451-462 ◽  
Author(s):  
Walid Aissa ◽  
Mostafa El-Sallak ◽  
Ahmed Elhakem
Keyword(s):  
Mass Flow Rate ◽  
Air Temperature ◽  
Mass Flow ◽  
Flow Rate ◽  
Air Flow ◽  
Ambient Air ◽  
Moisture Ratio ◽  
Convective Drying ◽  
Solar Dryer ◽  
Air Temperatures

Solar dryer chamber is designed and operated for five days of July 2008. Drying experiments are conducted for sponge-cotton; as a reference drying material in the ranges between 35.0 to 49.5?C of ambient air temperature, 35.2 to 69.8 ?C drying air temperature, 30 to 1258 W/m2 solar radiation and 0.016 to 0.08 kg/s drying air flow rate. For each experiment, the mass flow rate of the air remained constant throughout the day. The variation of moisture ratio, drying rate, overall dryer efficiency, and temperature distribution along the dryer chamber for various drying air temperatures and air flow rates are discussed. The results indicated that drying air temperature is the main factor in controlling the drying process and that air mass flow rate has remarkable influence on overall drying performance. For the period of operation, the dryer attained an average temperature of 53.68?C with a standard deviation of 8.49?C within a 12-h period from 7:00 h to 19:00 h. The results of this study indicated that the present drying system has overall efficiency between 1.85 and 18.6 % during drying experiments. Empirical correlations of temperature lapse and moisture ratio in the dryer chamber are found to satisfactorily describe the drying curves of sponge-cotton material which may form the basis for the development of solar dryer design charts.

A Screening Methodology for Climatic Evaluation of the Cooling Potential of Night Ventilation in Buildings

2012 ◽  
Author(s):  
Akhilesh Reddy Endurthy ◽  
T. Agami Reddy
Keyword(s):  
Network Models ◽  
Ambient Air ◽  
Reduction Factor ◽  
Thermal Mass ◽  
Preliminary Evaluation ◽  
Night Time ◽  
Air Temperatures ◽  
Detailed Simulation ◽  
Building Heat ◽  
Night Ventilation

Night ventilation is a well known strategy for passive cooling of residences and small commercial buildings. The building’s thermal mass can be cooled at night by ventilating the inside of the space with the relatively lower outdoor air temperatures, thereby lowering indoor temperatures during the warmer daytime period. Numerous experimental and theoretical studies have shown the effectiveness of the method to significantly reduce air conditioning loads or improve comfort levels in those climates where the night time ambient air temperature drops below that of the indoor air. One could develop/adapt computer programs with detailed mathematical component models to simulate and evaluate the performance of night ventilation strategies in a specific location for a particular building. A more basic problem is to develop a methodology whereby potential designers can screen various climatic locations and regions in order to perform a preliminary evaluation of which months of the year are good candidates for implementing such a scheme. Only after completion of such a phase is a detailed evaluation warranted for specific buildings. In this paper, effectiveness of night ventilation is quantified by a parameter called the Discomfort Reduction Factor (DRF) which is the index of reduction of occupant discomfort levels during the day time from night ventilation. Two different thermal network models which provide such insights are evaluated. Daily and monthly DRFs are calculated for two climate zones and three building heat capacities for the whole year. It is verified that night ventilation is effective in seasons and regions when day temperatures are between 30 °C and 36 °C and night temperatures are below 20 °C. The accuracy of these preliminary screening models may be lower than using a detailed simulation program but the loss in accuracy in using such tools is more than compensated by the insights provided, along with better transparency in the analysis approach and results obtained.

scholarly journals Experimental Investigation of the Air Exchange Effectiveness of Push-Pull Ventilation Devices

Energies ◽  
2020 ◽  
Vol 13 (21) ◽  
pp. 5817
Author(s):  
Sven Auerswald ◽  
Carina Hörberg ◽  
Thibault Pflug ◽  
Jens Pfafferott ◽  
Constanze Bongs ◽  
...  
Keyword(s):  
Heat Dissipation ◽  
Residential Buildings ◽  
Air Flow ◽  
Operation Mode ◽  
Ventilation System ◽  
Field Measurements ◽  
Gas Analysis ◽  
Decentralised Systems ◽  
Set Up ◽  
Air Exchange

The increasing installation numbers of ventilation units in residential buildings are driven by legal objectives to improve their energy efficiency. The dimensioning of a ventilation system for nearly zero energy buildings is usually based on the air flow rate desired by the clients or requested by technical regulations. However, this does not necessarily lead to a system actually able to renew the air volume of the living space effectively. In recent years decentralised systems with an alternating operation mode and fairly good energy efficiencies entered the market and following question was raised: “Does this operation mode allow an efficient air renewal?” This question can be answered experimentally by performing a tracer gas analysis. In the presented study, a total of 15 preliminary tests are carried out in a climatic chamber representing a single room equipped with two push-pull devices. The tests include summer, winter and isothermal supply air conditions since this parameter variation is missing till now for push-pull devices. Further investigations are dedicated to the effect of thermal convection due to human heat dissipation on the room air flow. In dependence on these boundary conditions, the determined air exchange efficiency varies, lagging behind the expected range 0.5 < εa < 1 in almost all cases, indicating insufficient air exchange including short-circuiting. Local air exchange values suggest inhomogeneous air renewal depending on the distance to the indoor apertures as well as the temperature gradients between in- and outdoor. The tested measurement set-up is applicable for field measurements.

Numerical Study of Internal Fire Whirls in a Kitchen With Ceiling Vents

2013 ◽  
Author(s):  
W. K. Chow ◽  
N. Cai ◽  
Y. Gao
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Numerical Study ◽  
Air Flow ◽  
Ventilation System ◽  
Necessary Condition ◽  
Temperature Distributions ◽  
Computational Fluid Dynamics Cfd ◽  
Fire Whirl ◽  
Set Up

The characteristics of flame rotation induced by a fire at the top of kitchen stove were studied numerically with Computational Fluid Dynamics (CFD). Four cases with different locations of fire sources and vents were set up; simulations of swirling air flow and temperature distributions in the kitchen room were carried out. Ventilation by ceiling vents was identified as the necessary condition for internal fire whirl. Recommendations on the design of kitchen ventilation system were made.

The Influence of the Phase Change Temperature Range and the Phase Change Hysteresis of a PCM on the Performance of an Air-PCM Heat Storage Unit

2019 ◽  
Author(s):  
Pavel Charvat ◽  
Martin Zalesak ◽  
Lubomir Klimes
Keyword(s):  
Phase Change ◽  
Heat Storage ◽  
Simulation Studies ◽  
Storage Unit ◽  
Maximum Phase ◽  
Phase Change Temperature ◽  
Temperature Range ◽  
Air Temperatures ◽  
Change Temperature ◽  
Melting And Solidification

Abstract The influence of the phase change temperature range and the hysteresis of the enthalpy-temperature relationship h(T) of PCMs on the performance of thermal energy storage (TES) systems is rarely quantified. In the present study, the quantification is done by the comparison of the amounts of heat stored in (and discharged from) the air-PCM heat exchanger (TES unit) operating between constant air temperatures. All simulations were conducted for the same mean phase change temperature of the PCM (30 °C). The inlet air temperature of the air-PCM HEX was 40 °C during the heat charging period and 20 °C during the heat discharge period. The maximum considered phase change temperature range of the PCM was 10 °C. The maximum phase transition hysteresis, in the study defined as the temperature difference between the melting and solidification peaks, was 4 °C. The results indicate that in case of the PCMs with a wide phase change temperature range and a significant hysteresis of the h(T) curves, the influence of these properties cannot be neglected in the simulation studies in order to achieve accurate results.

scholarly journals Effect of roughness geometry on heat transfer and friction characteristics of PCM storage unit for night coolness storage in summer season

2013 ◽  
Vol 17 (2) ◽  
pp. 365-375 ◽  
Author(s):  
Shailndra Shukla ◽  
Satish Singh
Keyword(s):  
Phase Change ◽  
Phase Change Material ◽  
Air Temperature ◽  
Flow Rate ◽  
Air Flow ◽  
Summer Season ◽  
Night Time ◽  
Storage Unit ◽  
Ambient Temperatures ◽  
Change Material

This paper presents a theoretical analysis of thermal storage unit using phase change material (PCM) as storage medium. Storage unit consists of parallel rectangular channels for the air flow which are separated by phase change storage material. The purpose of storage unit is to absorb the night coolness and to provide cooled air at comfort temperature during day time in summer season. MATLsimulation tool has been used to compute the air temperature variation with location as well as time, charging and discharging time of storage unit. Phase change material used for analysis is selected in such a way that it?s Melting point lies between comfort temperature and minimum night ambient temperatures. The air flow rate needed for charging of PCM is approximately four times greater than the flow rate required during day time to achieve comfort temperature for approximately eight hours, due to limited summer night time (only eight hours). The length of storage unit for which NTU value is greater than or equal to five will give the exit air temperature equal to PCM temperature for the case of latent heat utilization. It is found that artificial roughness on the duct surface effectively reduces the length of storage unit in the cost of some extra pressure drop across the duct.

Numerical Investigations of Outward Solidification in Cylindrical PCM Storage Unit

2015 ◽  
Vol 787 ◽  
pp. 177-181
Author(s):  
V. Antony Aroul Raj ◽  
C. Hariharan ◽  
R. Velraj ◽  
R.V. Seeniraj
Keyword(s):  
Ambient Air ◽  
Energy System ◽  
Night Time ◽  
Storage Unit ◽  
Cold Energy ◽  
Free Cooling ◽  
Implicit Finite Difference ◽  
Time Required ◽  
System Variables ◽  
Change Material

In the present work a transient numerical model is developed to investigate and predict the performance of a paraffin phase change material (PCM) in the annular portion of the cylindrical container during its solidification and melting processes. Enthalpy method of modeling is adopted and the discretised non-dimensional form of governing equations and boundary conditions are solved by implicit finite difference method by using MATLAB software. The temperature variation of PCM along two axes of the polar co-ordinates (r, z) and the time required for solidification are analyzed and presented. The effect of system variables on the performance of the Latent Heat Thermal Energy system ( LHTES) is studied. The model tested finds application in the concept of free cooling which is the process of storing the coldness of the night time ambient air in the LHTES in order to cool the building during the daytime by retrieving the stored cold energy.

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