Analytical model for the simulation of Trombe wall operation with heat storage

Passive solar systems, such as the Trombe wall, are cost-effective ways to reduce the energy consumption of buildings for heating, cooling, and ventilation. The operation of these systems can be simulated either with Building Energy Simulation Tools—BES like TRNSYS, EnergyPlus, etc either with Computational Fluid Dynamics—CFD. In both cases, the purchase of special software and/or special programming skills are required. In parallel analytical calculating tools are being developed, which also require some programming to solve an implicit system of non-linear equations but with fewer software requirements. The majority of analytical models concerns energy balance models for steady-state conditions with the result that heat storage is not taken into account, which in the case of a Trombe wall has a significant effect on the developed transport phenomena. In the present work, an analytical energy balance implicit model was developed for the simulation of the transient operation of a Trombe wall taking into account the heat storage. Using this model, the operation of a Trombe wall for 7 typical days of the year was simulated. The results are presented in terms of the daily evolution of the temperature with which the air enters the room served by the passive system, of the temperature of the Trombe wall surface adjacent to the served room, and of the airflow rate inside the air gap. These results are compared with the results that a system without heat storage would give. Both systems are assessed based on annual performance as calculated by a quasi-steady explicit model. The developed model can be used to calculate the operation of a Trombe wall as well as to supply explicit quasi-steady models with values for airflow rate inside the air gap for Trombe wall operation without mechanical ventilation. Feeding these values to a quasi-steady model developed by authors it was found that the increase of storage wall heat capacity, either changing the storage wall material, either using phase change materials, can offer better utilization of Trombe wall heat gains up to 35% yearly. Background: The present work aims to develop an analytical model for simulating the operation of a Trombe wall in a transient state taking into account the heat storage in the wall. Methods: A closed system of equations is developed, based on 5 energy balances and a series of assumptions and auxiliary relations, to calculate the operation of a wall Trombe with heat storage with an hourly time step. Results: Characteristics Trombe wall temperatures and mass flow rate through the air gap are calculated for typical days of 7 winter months. These are used for the calculation of utilizable heat gains from Trombe wall. Conclusions: The model that does not take into account heat storage predicts higher temperatures and air mass flow rate in the gap than the present model by 10%. However heat storage increase the utilizable heat gains by 35% compared with a system without heat storage.

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The Impact of Air Gap Width on the Free Thermal Load in the Trombe Wall Contains a Phase Change Material

Al-Kitab Journal for Pure Sciences ◽

10.32441/kjps.02.02.p18 ◽

2018 ◽

Vol 2 (2) ◽

pp. 264-275

Author(s):

Ehsan Abbas1 ◽

Shayma Aziz

Keyword(s):

Energy Storage ◽

Mass Flow Rate ◽

Mass Flow ◽

Flow Rate ◽

Storage System ◽

Weather Conditions ◽

Air Gap ◽

Trombe Wall ◽

Wood Frame ◽

The Impact

The objective of the present study is to investigate the effect of the air gap on the amount of mass flow rate and the ratio of energy storage in the thermal storage system containing a Trombe wall and that is through conducting experiments inside a room with dimensions of (1.5*1*1.5) m3, made of PVC sandwich insulation panel. The room contains a thermal wall of a dimension of (0.96*1.44*0.1) m3 made from a wood frame and contains 99 capsules of industrial wax of (6) cm diameter and (9.6) cm length, distributed by matrix form of (11*9). The wall is supported by four iron guides from both sides to move it easily in a distance of (10 to 35) cm from the glass cover in the south direction. The experiments have been conducted under real weather conditions of December 2016 for Kirkuk city, and this study included six widths of the air gap, arranged from (35 to 10) cm with steps of 5cm each. the results showed that the width of the air gap has a great effect on the mass flow rate through the air gap and energy incoming to the thermal system, where the best case for both factors was obtained at (b=35cm), and the max energy storage has been obtained at (b=15cm) and is about 45% of energy incoming to the system at the experiments of sunny days

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The Impact of Width of the Air Gap Channel on the Mass Flow Rate, Rayleigh Number, and Efficiency of Passive Solar Heating System

Tikrit Journal of Engineering Sciences ◽

10.25130/tjes.25.3.08 ◽

2018 ◽

Vol 25 (3) ◽

pp. 47-52 ◽

Cited By ~ 1

Author(s):

Ehsan F. Abbas ◽

Shayma A. Azat

Keyword(s):

Rayleigh Number ◽

Mass Flow Rate ◽

Mass Flow ◽

Flow Rate ◽

Winter Season ◽

Heating System ◽

Air Gap ◽

Trombe Wall ◽

Passive Solar ◽

The Impact

The mass flow rate and Rayleigh number has been investigated experimentally on the passive solar using Trombe wall consist of (industrial wax) used as phase change material (PCM). A test rig of a cubicle was made of PVC sandwich panel except the south wall, Trombe wall; covered with a clear glass of 6 mm thickness. The six experiments were carried out during the winter season in Kirkuk city with six different widths of the air gap channel (10, 15, 20, 25, 30, and 35) cm. The experimental resultts show that the mass flow rate proportional directly to a width of the channel and inversely with Rayleigh number. Moreover, the highest efficiency was obtained at a depth of 30 cm, where it was about 2.45 times the efficiency of 10 cm.

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Analytical Modeling and Experimental Validation of Heating at the Leaf Seal/Rotor Interface

Journal of Engineering for Gas Turbines and Power ◽

10.1115/1.4034702 ◽

2016 ◽

Vol 139 (4) ◽

Cited By ~ 1

Author(s):

Michael J. Pekris ◽

Gervas Franceschini ◽

Andrew K. Owen ◽

Terry V. Jones ◽

David R. H. Gillespie

Keyword(s):

Mass Flow Rate ◽

Analytical Model ◽

Mass Flow ◽

Flow Rate ◽

Temperature Rise ◽

Thermal Characteristic ◽

Frictional Heat ◽

Test Facility ◽

Engine Operation ◽

Secondary Air

The secondary air system of a modern gas or steam turbine is configured to satisfy a number of requirements, such as to purge cavities and maintain a sufficient flow of cooling air to key engine components, for a minimum penalty on engine cycle efficiency and specific fuel consumption. Advanced sealing technologies, such as brush seals and leaf seals, are designed to maintain pressures in cavities adjacent to rotating shafts. They offer significant reductions in secondary air parasitic leakage flows over the legacy sealing technology, the labyrinth seal. The leaf seal comprises a series of stacked sheet elements which are inclined relative to the radial direction, offering increased axial rigidity, reduced radial stiffness, and good leakage performance. Investigations into leaf seal mechanical and flow performance have been conducted by previous researchers. However, limited understanding of the thermal behavior of contacting leaf seals under sustained shaft contact has led to the development of an analytical model in this study, which can be used to predict the power split between the leaf and rotor from predicted temperature rises during operation. This enables the effects of seal and rotor thermal growth and, therefore, implications on seal endurance and rotor mechanical integrity to be quantified. Consideration is given to the heat transfer coefficient in the leaf pack. A dimensional analysis of the leaf seal problem using the method of extended dimensions is presented, yielding the expected form of the relationship between seal frictional power generation, leakage mass flow rate, and rotor temperature rise. An analytical model is derived which is in agreement. Using the derived leaf temperature distribution formula, the theoretical leaf tip temperature rise and temperature distributions are computed over a range of mass flow rates and frictional heat values. Experimental data were collected in high-speed tests of a leaf seal prototype using the Engine Seal Test Facility at Oxford University. These data were used to populate the analytical model and collapsed well to confirm the expected linear relationship. In this form, the thermal characteristic can be used with predictions of mass flow rate and frictional power generated to estimate the leaf tip and rotor temperature rise in engine operation.

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Analytical Modeling and Experimental Validation of Heating at the Leaf Seal/Rotor Interface

Volume 5A: Heat Transfer ◽

10.1115/gt2016-57577 ◽

2016 ◽

Cited By ~ 1

Author(s):

Michael J. Pekris ◽

Gervas Franceschini ◽

Andrew K. Owen ◽

Terry V. Jones ◽

David R. H. Gillespie

Keyword(s):

Mass Flow Rate ◽

Analytical Model ◽

Mass Flow ◽

Flow Rate ◽

Temperature Rise ◽

Thermal Characteristic ◽

Frictional Heat ◽

Test Facility ◽

Engine Operation ◽

Secondary Air

The secondary air system of a modern gas or steam turbine is configured to satisfy a number of requirements, such as to purge cavities and maintain a sufficient flow of cooling air to key engine components, for a minimum penalty on engine cycle efficiency and specific fuel consumption. Advanced sealing technologies, such as brush seals and leaf seals, are designed to maintain pressures in cavities adjacent to rotating shafts. They offer significant reductions in secondary air parasitic leakage flows over the legacy sealing technology, the labyrinth seal. The leaf seal comprises a series of stacked sheet elements which are inclined relative to the radial direction, offering increased axial rigidity reduced radial stiffness, and good leakage performance. Investigations into leaf seal mechanical and flow performance have been conducted by previous researchers. However, limited understanding of the thermal behavior of contacting leaf seals under sustained shaft contact has led to the development of an analytical model in this study, which can be used to predict the power split between the leaf and rotor from predicted temperature rises during operation. This enables the effects of seal and rotor thermal growth and, therefore, implications on seal endurance and rotor mechanical integrity to be quantified. Consideration is given to the heat transfer coefficient in the leaf pack. A dimensional analysis of the leaf seal problem using the method of extended dimensions is presented, yielding the expected form of the relationship between seal frictional power generation, leakage mass flow rate and rotor temperature rise. An analytical model is derived which is in agreement. Using the derived leaf temperature distribution formula, the theoretical leaf tip temperature rise and temperature distributions are computed over a range of mass flow rates and frictional heat values. Experimental data were collected in high speed tests of a leaf seal prototype using the Engine Seal Test Facility at Oxford University. These data were used to populate the analytical model, and collapsed well to confirm the expected linear relationship. In this form, the thermal characteristic can be used with predictions of mass flow rate and frictional power generated to estimate leaf tip and rotor temperature rise in engine operation.

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Experimental Study of Artificial Solar Air Heater Using Trapezoidal Wave Plate

R E M (Rekayasa Energi Manufaktur) Jurnal ◽

10.21070/r.e.m.v4i2.806 ◽

2019 ◽

Vol 4 (2) ◽

pp. 135-148

Author(s):

Lohdy Diana ◽

Arrad Ghani Safitra ◽

Muhammad Syarifuddin Firmansyah ◽

Mishbaakhus Prana Zinedine

Keyword(s):

Mass Flow Rate ◽

Mass Flow ◽

Flow Rate ◽

Airflow Rate ◽

Halogen Lamp ◽

Solar Air Heater ◽

Air Mass ◽

Wave Plate ◽

Air Heater ◽

Air Heating

A solar air heater is needed for the drying process, especially in Indonesia. It means the researches to produce a solar air heater that had high performance is necessary. This research analyses the performance of solar air heater using trapezoidal absorber plate with variation of folded angle 83˚, 85˚, and 87˚. The research carry out artificial experimentally using halogen lamp as a solar simulator. The working principle of solar air heating begins with an induction fan sucking air to enter through the honeycomb then flowing into the air heating duct. The process of heat transfer occurs in a halogen heat lamp passed by the transparent glass and then absorbed by the absorbent plate. This heat will heat the air flowing in the air heating pipe to be transmitted into the drying cupboard. The experiment used several variations of the mass airflow rate 0.022 until 0.051 kg/s and intensity 850, 900, dan 950 W/m2. Temperature measurement is carried out by installing a thermocouple at several points that have been determined. The best performance produced by the wave plate-shaped trapezoidal wave heaters 83˚ when I = 950 W/m2 air mass flow rate 0.022 kg/s with the temperature of the absorbent plate 87 ˚C, the temperature of the exit air 43.2 ˚C, the difference in the rise in air temperature 15.2 ˚C, and when I = 950 W/m2 air mass flow rate 0.051 kg/s the useful heat generated by the air heater 527 Watt, and thermal efficiency 96.8%.

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Experimental study of an ultrasonic regenerative evaporative cooler for a desiccant cooling system

Building Services Engineering Research and Technology ◽

10.1177/0143624418810934 ◽

2018 ◽

Vol 40 (2) ◽

pp. 151-175 ◽

Cited By ~ 5

Author(s):

BS Arun ◽

V Mariappan

Keyword(s):

Mass Flow Rate ◽

Mass Flow ◽

Flow Rate ◽

Cooling System ◽

Cooling Capacity ◽

Water Mist ◽

Extraction Ratio ◽

Feed Water ◽

Airflow Rate ◽

Evaporative Cooler

This paper presents fabrication of an ultrasonic regenerative evaporative cooler, coupled with a desiccant dehumidifier. Ultrasonic regenerative evaporative cooler consists of several sets of a dry channel and a wet channel. A part of the air from the dry channel is redirected into the wet channel where it is cooled by evaporation of water mist from an ultrasonic atomiser. Air flowing through dry channels is pre-cooled by heat transfer between wet and dry channels, without changing its humidity. In this cooler, the conventional hygroscopic layer for wetting the plate surface is replaced with the water mist. It is observed that the performance of the cooling system significantly depends on the channel spacing, channel length, inlet airflow rate and extraction ratio, and marginally depends upon feed water temperature. The room cooling capacity is eminently responsive to both air mass flow rate and extraction ratio. The maximum available room cooling capacity of 339.8 W is obtained for the optimal values of 0.0488 kg/s mass flow rate of air and 0.37 extraction ratio. The prototype achieved wet-bulb effectiveness values as high as 1.15 and delivered more than 10℃ temperature drop. Practical application: An ultrasonic regenerative evaporative cooler can be coupled with a desiccant dehumidification unit for use in hot and humid climate to achieve comfort condition utilising less energy and feed water when compared to the vapour compression refrigeration system. From this prototype researchers and engineers can develop, by combining desiccant regenerators and evaporative coolers which use ultrasonic method for low-temperature dehydration of desiccant substance. Solar thermal energy can also be directly utilised for marginally heating the desiccant substance during the regeneration process. Overall, this system can contribute to the development of energy efficient buildings.

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Computer Aided Design Studies of a Multiple Cylinder Refrigeration Compressor

Journal of Mechanical Design ◽

10.1115/1.3453975 ◽

1978 ◽

Vol 100 (4) ◽

pp. 599-603

Author(s):

J. F. Hamilton ◽

D. D. Schwerzler

Keyword(s):

Mass Flow Rate ◽

Analytical Model ◽

Mass Flow ◽

Flow Rate ◽

Computer Aided Design ◽

Gas Flow ◽

Temperature Drop ◽

Flow Process ◽

The Common ◽

Thermodynamic Processes

A multi-cylinder refrigerant compressor was analytically modeled and simulated on a digital computer. The modeling includes the kinematics of the mechanical compressor, the thermodynamic processes in the cylinders and the flow process of the refrigerant gas in and out of the cylinders. In addition the modeling includes the valve dynamics in controlling the gas flow, the thermodynamic processes in the common suction and discharge plenums and the interaction of the cylinder processes through the common plenums. The remainder of the refrigeration system was treated as pressure-temperature drop. The analytical model was compared to experimental data in terms of cylinder pressures, suction-discharge plenum pressures and temperatures, valve motions and the average mass flow rate of the refrigerant gas. The correlation between the comparison variable was quite good with some error in the prediction of suction valve closing time. The analytical model was used to predict the effect of increased compressor speed on the performance of the compressor. The speed was increased from 500 rpm to 2700 rpm with a decrease in volumetric efficiency from 87 percent to 60 percent, an increase in mass flow rate from 0.0378 kg/s to 0.151 kg/s. Valve impact speeds were also calculated to predict degradation in valve life.

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INVESTIGATION OF COMBINATION BETWEEN LATENT AND SENSIBLE HEAT STORAGE MATERIALS ON THE PERFORMANCE OF FLAT PLATE SOLAR AIR HEATER

THE IRAQI JOURNAL FOR MECHANICAL AND MATERIALS ENGINEERING ◽

10.32852/iqjfmme.vol18.iss1.73 ◽

2018 ◽

Vol 18 (1) ◽

pp. 63-77

Author(s):

Akram H Abed ◽

Abdulmunem R Abdulmunem

Keyword(s):

Flat Plate ◽

Mass Flow Rate ◽

Mass Flow ◽

Flow Rate ◽

Heat Storage ◽

Paraffin Wax ◽

Solar Air Heater ◽

Storage Materials ◽

Air Heater ◽

Heat Storage Materials

In this work, a combination between latent heat storage materials (LHSm) and sensibleheat storage materials (SHSm) as new storage heat material in flat plate solar air heater wastested experimentally. PCM (paraffin wax) at a certain ratios (10%) and (20%) were used asLHSm with a pure cement (base material) as SHSm. The experimental tests was doneindoor at irradiance of (1000W/m2) with forced convection, the mass flow rate of air are(0.5kg/min) and (1.13kg/min). The results indicated that the enhancing thermo-physicalproperties of adding pure cement by a certain ratios of paraffin wax led to enhancement inthermal energy stored. The percentage increasing in storage heat duration time was (29%)for compound cement with (10%PCM), (38.4%) for compound cement with (20%PCM),compared with pure cement at (0.5kg/min) air mass flow rate. And at (1.13kg/min) air massflow rate, it was (33.3%) for compound cement with (10%PCM) and (52.6%) for compoundcement with (20%PCM) compared with pure cement.

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