Theoretical study of the effect of liquid desiccant mass flow rate on the performance of a cross flow parallel-plate liquid desiccant-air dehumidifier

2013 ◽  
Vol 49 (11) ◽  
pp. 1587-1593 ◽  
Author(s):  
Abdulrahman Th. Mohammad ◽  
Sohif Bin Mat ◽  
M. Y. Sulaiman ◽  
K. Sopian ◽  
Abduljalil A. Al-abidi
Keyword(s):  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Parallel Plate ◽  
Theoretical Study ◽  
Cross Flow ◽  
Liquid Desiccant

Transient Response of a Cross Flow Heat Exchanger Subjected to Temperature and Flow Perturbations

2015 ◽  
Author(s):  
Karthik Silaipillayarputhur ◽  
Stephen A. Idem
Keyword(s):  
Heat Exchanger ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Heat Exchangers ◽  
Cross Flow ◽  
Transient Performance ◽  
Numerical Predictions ◽  
Minimum Capacity ◽  
Flow Heat

The transient performance of a multi-pass cross flow heat exchanger subjected to temperature and mass flow rate perturbations, where the heat exchanger flow circuiting is neither parallel flow nor counter flow, is considered in this work. A detailed numerical study was performed for representative single-pass, two-pass, and three-pass heat exchangers. Numerical predictions were obtained for cases where the minimum capacity rate fluid was subjected to a step change in inlet temperature in absence of mass flow rate perturbations. Likewise, numerical predictions were obtained for the heat exchangers operating initially at steady state, where a step mass flow rate change of the minimum capacity rate fluid was imposed in the absence of any fluid temperature perturbations. The transient performance of this particular heat exchanger configuration subjected to these temperature and flow disturbances has not been discussed previously in the available literature. In the present study the energy balance equations for the hot and cold fluids and the heat exchanger wall were solved using an implicit central finite difference method. A parametric study was conducted by varying the dimensionless quantities that govern the transient response of the heat exchanger over a typical range of values. Because of the storage of energy in the heat exchanger wall, and finite propagation times associated with the inlet perturbations, the outlet temperatures of both fluids do not respond instantaneously. The results are compared with previously published transient performance predictions of multi-pass counter flow and parallel flow heat exchangers.

scholarly journals Multiple Impinging Jet Air-Assisted Atomization

2017 ◽  
Author(s):  
Mário Costa ◽  
Bruno Pizziol ◽  
Miguel Panao ◽  
André Silva
Keyword(s):  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Alternative Fuels ◽  
Fossil Fuels ◽  
Cross Flow ◽  
Liquid Sheet ◽  
Air Mass ◽  
Breakup Mechanism ◽  
The Impact

The growth of the aviation sector triggered the search for alternative fuels and continued improvements in thecombustion process. This work addresses the technological challenges associated with spray systems and theconcern of mixing biofuels with fossil fuels to produce alternative and more ecological fuels for aviation. This workproposes a new injector design based on sprays produced from the simultaneous impact of multiple jets, using anadditional jet of air to assist the atomization process. The results evidence the ability to control the average dropsize through the air-mass flow rate. Depending on the air-mass flow rate there is a transition between atomizationby hydrodynamic breakup of the liquid sheet formed on the impact point, to an aerodynamic breakup mechanism,as found in the atomization of inclined jets under cross-flow conditions. The aerodynamic shear breakupdeteriorates the atomization performance, but within the same order of magnitude. Finally, our experiments showthat mixing a biofuel with a fossil fuel does not significantly alter the spray characteristics, regarded as a stepfurther in developing alternative and more ecological fuels for aero-engines.DOI: http://dx.doi.org/10.4995/ILASS2017.2017.4737

Review and Analysis of Cross Flow Heat Exchanger Transient Modeling for Flow Rate and Temperature Variations

2015 ◽  
Vol 7 (4) ◽  
Author(s):  
Tianyi Gao ◽  
James Geer ◽  
Bahgat Sammakia
Keyword(s):  
Heat Exchanger ◽  
Mass Flow Rate ◽  
Transient Response ◽  
Mass Flow ◽  
Flow Rate ◽  
Heat Exchangers ◽  
Cross Flow ◽  
Inlet Temperature ◽  
Flow Rate Change ◽  
Flow Heat

Heat exchangers are important facilities that are widely used in heating, ventilating, and air conditioning (HVAC) systems. For example, heat exchangers are the primary units used in the design of the heat transfer loops of cooling systems for data centers. The performance of a heat exchanger strongly influences the thermal performance of the entire cooling system. The prediction of transient phenomenon of heat exchangers is of increasing interest in many application areas. In this work, a dynamic thermal model for a cross flow heat exchanger is solved numerically in order to predict the transient response under step changes in the fluid mass flow rate and the fluid inlet temperature. Transient responses of both the primary and secondary fluid outlet temperatures are characterized under different scenarios, including fluid mass flow rate change and a combination of changes in the fluid inlet temperature and the mass flow rate. In the ε-NTU (number of transfer units) method, the minimum capacity, denoted by Cmin, is the smaller of Ch and Cc. Due to a mass flow rate change, Cmin may vary from one fluid to another fluid. The numerical procedure and transient response regarding the case of varying Cmin are investigated in detail in this study. A review and comparison of several journal articles related to the similar topic are performed. Several sets of data available in the literatures which are in error are studied and analyzed in detail.

scholarly journals Modeling And Fouling Detection Of The Aircraft Environmental Control System Heat Exchanger

2021 ◽  
Author(s):  
Shoaib A. Shah
Keyword(s):  
Control System ◽  
Heat Exchanger ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Environmental Control ◽  
Cross Flow ◽  
The State ◽  
The Core ◽  
On Line

A Diagnostics, Prognostics and Health Management (DPHM) solution is proposed for the operation of the aircraft environmental control system (ECS) cross flow heat exchanger. In particular, a dynamic model is derived and applied to on-line detection of fouling in the aircraft ECS cross flow plate-and-fin heat exchanger. Predictive maintenance actions can be scheduled as per the on-line detected fouling status of the specific component, supporting condition based maintenance. The heat exchanger model is of the lumped state space form, where the state consists of the core and fin temperatures. The ratios of the thermal capacities of the masses of the two air streams to the thermal capacity of the core itself are neglected, and the model parameters' functional dependency on mass flow rate and influence of secondary surfaces (fins) are taken into account in order to accurately describe the dynamic behavior of the heat exchanger. Since the parameters are functions of mass flow rate, as are the core and fin temperatures, and the model is nonlinear in the state variables, an extended Kalman filtering (EKF) algorithm is applied to estimate the state dependent parameters. The effectiveness of the model's formulation is supported by the quality of the corresponding predicted results, which in turn are validated via experimental tests.

A Study of the Performance of a Hybrid Liquid Desiccant Cooling System Using Lithium Chloride

2003 ◽  
Vol 125 (1) ◽  
pp. 129-131 ◽  
Author(s):  
Pedro Mago ◽  
D. Yogi Goswami
Keyword(s):  
Mass Flow Rate ◽  
Field Test ◽  
Mass Flow ◽  
Flow Rate ◽  
Air Conditioning ◽  
Cooling System ◽  
Liquid Desiccant ◽  
Test House ◽  
Vapor Compression System ◽  
Research And Education

This paper presents field test of a hybrid solar liquid desiccant cooling system conducted at a test house at the University of Florida’s Energy Research and Education Park. These tests consisted of operating the air conditioning system at the test house in two configurations: the conventional vapor compression system and the hybrid desiccant system. Experiments were conducted to study the influence of the air mass flow rate, temperature of the inlet air, temperature of the desiccant, and desiccant mass flow rate on the performance of both system configurations. Based on the field test results, it was found that the hybrid desiccant system improves the air conditioning performance in the field test house by decreasing the outlet humidity and temperature of the air.

scholarly journals Numerical Investigation of Parameters Affecting the Thermal and Hydrodynamic Characteristics of Impinging Jets in Cross Flow

1970 ◽  
Vol 1 (1) ◽  
Author(s):  
B. M. Suloiman ◽  
B. A. Jubran
Keyword(s):  
Numerical Investigation ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Velocity Ratio ◽  
Cross Flow ◽  
Impinging Jets ◽  
Minor Effect ◽  
Vortex Strength ◽  
Effective Velocity

In this investigation the hydrodynamic and the thermal fields due to a single impinging jet in cross-flow have been investigated numerically, using a 2-D axisymmetric model in order to predict the ground vortex characteristics. The parameters investigated include the effective velocity ratio, the nozzle height, the nozzle pressure ratio, the intake location, the intake mass flow rate and the jet temperature ratio. It is interesting to note that even with the 2-D modeling limitations it was possible to capture most of the thermal and fluid field characteristics of the ground vortex. It was found that the temperature distribution in the flow field is greatly affected by the effective velocity, and the maximum penetration point of the ground vortex is equal to the hot gas penetration. The ground vortex strength increases slightly with increasing the intake mass flow rate but has a minor effect on the ground vortex geometry and on the penetration of the hot gases. The intake location has a significant effect on the ground vortex strength when it is located upstream of the ground vortex core. Key Words: Numerical investigation, Turbulence Models, Impinging jets, Cross-flow.

scholarly journals Modeling And Fouling Detection Of The Aircraft Environmental Control System Heat Exchanger

2021 ◽  
Author(s):  
Shoaib A. Shah
Keyword(s):  
Control System ◽  
Heat Exchanger ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Environmental Control ◽  
Cross Flow ◽  
The State ◽  
The Core ◽  
On Line

A Diagnostics, Prognostics and Health Management (DPHM) solution is proposed for the operation of the aircraft environmental control system (ECS) cross flow heat exchanger. In particular, a dynamic model is derived and applied to on-line detection of fouling in the aircraft ECS cross flow plate-and-fin heat exchanger. Predictive maintenance actions can be scheduled as per the on-line detected fouling status of the specific component, supporting condition based maintenance. The heat exchanger model is of the lumped state space form, where the state consists of the core and fin temperatures. The ratios of the thermal capacities of the masses of the two air streams to the thermal capacity of the core itself are neglected, and the model parameters' functional dependency on mass flow rate and influence of secondary surfaces (fins) are taken into account in order to accurately describe the dynamic behavior of the heat exchanger. Since the parameters are functions of mass flow rate, as are the core and fin temperatures, and the model is nonlinear in the state variables, an extended Kalman filtering (EKF) algorithm is applied to estimate the state dependent parameters. The effectiveness of the model's formulation is supported by the quality of the corresponding predicted results, which in turn are validated via experimental tests.

A Study of the Performance of a Hybrid Liquid Desiccant Cooling System Using Lithium Chloride

2001 ◽  
Author(s):  
Pedro Mago ◽  
D. Yogi Goswami
Keyword(s):  
Mass Flow Rate ◽  
Field Test ◽  
Lithium Chloride ◽  
Mass Flow ◽  
Flow Rate ◽  
Air Conditioning ◽  
Cooling System ◽  
Field Tests ◽  
Liquid Desiccant ◽  
Test House

Abstract A hybrid desiccant system using aqueous lithium chloride was studied by simulation, laboratory test, and field tests. This paper presents field test of a hybrid solar liquid desiccant cooling system conducted at a test house at the University of Florida’s Energy Research and Education Park. These tests consisted of operating the air conditioning system at the test house in two configurations: the conventional vapor compression system and the hybrid desiccant system. For each configuration the system was operated in two modes: recirculation, and 100% ventilation air. Experiments were conduct to study the influence of the air mass flow rate, temperature of the inlet air, temperature of the desiccant, and desiccant mass flow rate on the performance of both system configurations. Based on the field test results it was found that the hybrid desiccant system improves the air conditioning performance in the field test house by decreasing the outlet humidity and temperature of the air. It was also found that the hybrid desiccant cooling system is more cost effective for the case 100% fresh air ventilation than recirculation.

Theoretical Study of New Configuration of Photovoltaic/Thermal Solar Collector (PV/T) Design

2013 ◽  
Vol 772 ◽  
pp. 681-687 ◽  
Author(s):  
M.I. Fadhel ◽  
Sakhr M. Sultan ◽  
Saqaff Ahmed Alkaff
Keyword(s):  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Solar Collector ◽  
Theoretical Study ◽  
Spiral Flow ◽  
Absorber Plate ◽  
Insulating Material ◽  
Pv Panel ◽  
T System

The combination of solar thermal and PV technologies leads to form a single module called PVT system. This system is able to produce heat and electricity simultaneously. In this paper, a new configuration and design of PV/T system are proposed, and a theoretical study of this system is evaluated. The PV/T consists of certain layers which are the glass, air gap, PV panel, absorber plate and insulating material layer. The monocrystalline PV and spiral flow absorber plate are used in this study. The results of the system performance under typical sunny climatic Malaysian condition are presented. The maximum thermal and electrical efficiencies obtained are 64.4 % and 12.13%, respectively. The effect of mass flow rate on the outlet water temperature is also evaluated. It is shown that the optimum mass flow rate for the designed system is between 0.005 and 0.075 kg/s.

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