scholarly journals Modeling of a PCM TES Tank Used as an Alternative Heat Sink for a Water Chiller. Analysis of Performance and Energy Savings

Energies ◽  
2019 ◽  
Vol 12 (19) ◽  
pp. 3652 ◽  
Author(s):  
Real-Fernández ◽  
Navarro-Esbrí ◽  
Mota-Babiloni ◽  
Barragán-Cervera ◽  
Domenech ◽  
...  
Keyword(s):  
Ambient Temperature ◽  
Heat Sink ◽  
Phase Change Materials ◽  
Energy Savings ◽  
Energy Performance ◽  
Coefficient Of Performance ◽  
Maximum Deviation ◽  
Outlet Temperature ◽  
Vapor Compression ◽  
Transient Model

Phase change materials (PCMs) can be used in refrigeration systems to redistribute the thermal load. The main advantages of the overall system are a more stable energy performance, energy savings, and the use of the off-peak electric tariff. This paper proposes, models, tests, and analyzes an experimental water vapor compression chiller connected to a PCM thermal energy storage (TES) tank that acts as an alternative heat sink. First, the transient model of the chiller-PCM system is proposed and validated through experimental data directly measured from a test bench where the PCM TES tank is connected to a vapor compression-based chiller. A maximum deviation of 1.2 °C has been obtained between the numerical and experimental values of the PCM tank water outlet temperature. Then, the validated chiller-PCM system model is used to quantify (using the coefficient of performance, COP) and to analyze its energy performance and its dependence on the ambient temperature. Moreover, electrical energy saving curves are calculated for different ambient temperature profiles, reaching values between 5% and 15% taking the experimental system without PCM as a baseline. Finally, the COP of the chiller-PCM system is calculated for different temperatures and use scenarios, and it is compared with the COP of a conventional aerothermal chiller to determine the switch ambient temperature values for which the former provides energy savings over the latter.

scholarly journals A Comparative Analysis of Thermoelectric Modules for the Purpose of Ensuring Thermal Comfort in Protective Clothing

2021 ◽  
Vol 11 (17) ◽  
pp. 8068
Author(s):  
Anna Dąbrowska ◽  
Monika Kobus ◽  
Bartosz Pękosławski ◽  
Łukasz Starzak
Keyword(s):  
Heat Flux ◽  
Ambient Temperature ◽  
Heat Sink ◽  
Protective Clothing ◽  
Phase Change Materials ◽  
Thermoelectric Module ◽  
Thermoelectric Modules ◽  
Cooling Function ◽  
A Tec ◽  
Flexible Thermoelectric

In recent times, more and more workers are exposed to thermal stress due to climate changes and increased ambient temperature. Demanding physical activities and the use of protective clothing are additional sources of thermal load for workers. Therefore, recent research has focused on the development of protective clothing with a cooling function. Phase change materials, air or liquid, were mainly used for this purpose; only a few publications were concerned the use of thermoelectric modules. This publication analyzes the influence of such factors as supplied current, ambient temperature, and the type of heat sink on the amount of heat flux transferred by a thermoelectric cooler (TEC) and the electric power consumed by it. In the course of laboratory tests, a flexible thermoelectric module and three heat sink variants were tested. For this purpose, a polymer TEGway heat sink, a metal one, and a self-made one based on a superabsorbent were used. The research showed that at a temperature of 30 °C and above, the amount of the heat flux transferred by a TEC with a total area of 58 cm2, and an active area of 10 cm2 should be expected to be from 1 W to 1.5 W. An increase in ambient temperature from 20 to 35 °C caused a significant reduction in the heat flux by about 1 W. The results obtained indicated that the type of heat sink affects the heat flux drawn by the TEC to a statistically significant extent. The heat sink using the evaporation effect turned out to be the most efficient.

scholarly journals Comparison Evaluations of VRF and RTU Systems Performance on Flexible Research Platform

2018 ◽  
Vol 2018 ◽  
pp. 1-16 ◽  
Author(s):  
Je-hyeon Lee ◽  
Piljae Im ◽  
Jeffrey D. Munk ◽  
Mini Malhotra ◽  
Min-seok Kim ◽  
...  
Keyword(s):  
Energy Use ◽  
Energy Savings ◽  
Thermal Conditions ◽  
The United States ◽  
Energy Performance ◽  
Coefficient Of Performance ◽  
Part Load ◽  
Variable Air Volume ◽  
Heating And Cooling ◽  
Load Conditions

The energy performance of a variable refrigerant flow (VRF) system was evaluated using an occupancy-emulated research building in the southeastern region of the United States. Full- and part-load performance of the VRF system in heating and cooling seasons was compared with a conventional rooftop unit (RTU) variable-air-volume system with electric resistance heating. During both the heating and cooling seasons, full- and part-load conditions (i.e., 100%, 75%, and 50% thermal loads) were maintained alternately for 2 to 3 days each, and the energy use, thermal conditions, and coefficient of performance (COP) for the RTU and VRF system were measured. During the cooling season, the VRF system had an average COP of 4.2, 3.9, and 3.7 compared with 3.1, 3.0, and 2.5 for the RTU system under 100%, 75%, and 50% load conditions and resulted in estimated energy savings of 30%, 37%, and 47%, respectively. During the heating season, the VRF system had an average COP ranging from 1.2 to 2.0, substantially higher than the COPs of the RTU system, and resulted in estimated energy savings of 51%, 47%, and 27% under the three load conditions, respectively.

From Chip to Cooling Tower Data Center Modeling: Influence of Chip Temperature Control Philosophy

2011 ◽  
Vol 133 (3) ◽  
Author(s):  
Ed J. Walsh ◽  
Thomas J. Breen ◽  
Jeff Punch ◽  
Amip J. Shah ◽  
Cullen E. Bash
Keyword(s):  
Heat Sink ◽  
Data Center ◽  
Energy Performance ◽  
Coefficient Of Performance ◽  
Control Algorithms ◽  
Cooling Power ◽  
Operational Strategies ◽  
The Impact ◽  
Heat Sink Temperature

The chiller cooled data center environment consists of many interlinked elements that are usually treated as individual components. This chain of components and their influences on each other must be considered in determining the benefits of any data center design and operational strategies seeking to improve efficiency, such as temperature controlled fan algorithms. Using the models previously developed by the authors, this paper extends the analysis to include the electronics within the rack through considering the processor heat sink temperature. This has allowed determination of the influence of various cooling strategies on the data center coefficient of performance. The strategy of increasing inlet aisle temperature is examined in some detail and found not to be a robust methodology for improving the overall energy performance of the data center, while tight temperature controls at the chip level consistently provide better performance, yielding more computing per watt of cooling power. These findings are of strong practical relevance for the design of fan control algorithms at the rack level and general operational strategies in data centers. Finally, the impact of heat sink thermal resistance is considered, and the potential data center efficiency gains from improved heat sink designs are discussed.

scholarly journals A NUMERICAL SOLUTION THAT DETERMINES THE TEMPERATURE FIELD INSIDE PHASE CHANGE MATERIALS: APPLICATION IN BUILDINGS

2013 ◽  
Vol 19 (4) ◽  
pp. 518-528 ◽  
Author(s):  
Giuseppina Ciulla ◽  
Valerio Lo Brano ◽  
Antonio Messineo ◽  
Giorgia Peri
Keyword(s):  
Phase Change ◽  
Numerical Solution ◽  
Building Materials ◽  
Phase Change Materials ◽  
Energy Savings ◽  
Transfer Problem ◽  
Energy Performance ◽  
Wall Layer ◽  
Storage Device ◽  
Thermal Mass

The use of novel building materials that contain active thermal components would be a major advancement in achieving significant heating and cooling energy savings. In the last 40 years, Phase Change Materials or PCMs have been tested as thermal mass components in buildings, and most studies have found that PCMs enhance the building energy performance. The use of PCMs as an energy storage device is due to their relatively high fusion latent heat; during the melting and/or solidification phase, a PCM is capable of storing or releasing a large amount of energy. PCMs in a wall layer store solar energy during the warmer hours of the day and release it during the night, thereby decreasing and shifting forward in time the peak wall temperature. In this paper, an algorithm is presented based on the general Fourier differential equations that solve the heat transfer problem in multi-layer wall structures, such as sandwich panels, that includes a layer that can change phase. In detail, the equations are proposed and transformed into formulas useful in the FDM approach (finite difference method), which solves the system simultaneously for the temperature at each node. The equation set proposed is accurate, fast and easy to integrate into most building simulation tools in any programming language. The numerical solution was validated using a comparison with the Voller and Cross analytical test problem.

scholarly journals Experimental Study of the Thermal Behavior of a Watercress Planted Roofed Cubic Cell to be Watered with Domestic Wastewater

2021 ◽  
pp. 19-30
Author(s):  
Dominique Morau ◽  
Ives Abel Fetra Andriatsitohaina Rabesah ◽  
Hery Tiana Rakotondramiarana
Keyword(s):  
Thermal Conductivity ◽  
Thermal Behavior ◽  
Ambient Temperature ◽  
Energy Savings ◽  
Domestic Wastewater ◽  
Energy Performance ◽  
Conventional Concrete ◽  
Apparent Thermal Conductivity ◽  
Fluctuation Amplitude

One of the virtues of watercress is its ability to grow in wastewater. This work aims at experimentally studying the thermal behavior of a watercress planted roofed cubic cell. To do this, the temperatures of various components of the cell and the solar radiation received by this cell were measured in order to compare the watercress roof performance with that of the conventional concrete roof. Then, the influence of the opening applied on the door of the studied cell was analyzed. As results, the fluctuation amplitude of the indoor ambient temperature of the concrete roofed cell is wider than that of the green roofed cell. Moreover, the last opening applied to the facades of the cell was the optimum area that the ambient temperature indoor was more attenuated. The LAI’s crop was worth 1.2. In addition, the low value of the canopy apparent thermal conductivity revealed that this layer plays a role of thermal insulation. The rooftop greening allows energy savings of about 85% compared to the consumed energy with conventional roofing. An extension of this work could be the energy performance analysis of a system using renewable energy for pumping domestic wastewater produced in or around green roofed housing.

Enhancing the Performance of the Building’s Vapor Compression Air Cooling System Using Earth-Air Heat Exchanger

2017 ◽  
Author(s):  
Fadi A. Ghaith ◽  
Fadi J. Alsouda
Keyword(s):  
Heat Exchanger ◽  
Soil Temperature ◽  
Air Temperature ◽  
Cooling System ◽  
Ambient Air ◽  
Coefficient Of Performance ◽  
Maximum Deviation ◽  
Air Cooling ◽  
Vapor Compression ◽  
Air Cooling System

This paper aims to evaluate the thermal performance and feasibility of integrating the Earth-Air Heat Exchanger (EAHE) with the building’s vapor compression air cooling system. In the proposed system, the ambient air is forced by an axial fan through an EAHE buried at a certain depth below the ground surface. EAHE uses the subsoil low temperature and soil thermal properties to reduce the air temperature. The outlet air from the EAHE was used for the purpose of cooling the condenser of the vapor compression cycle (VCC) to enhance its coefficient of performance (COP). The potential enhancement on the COP was investigated for two different refrigerants (i.e. R-22 and R410a) cooling systems. A mathematical model was developed to estimate the underground soil temperature at different depths and the corresponding outlet air temperature of EAHE was calculated. The obtained results showed that the soil temperature in Dubai at 4 meters depth is about 27°C and remains relatively constant across the year. In order to estimate the effect of using EAHE on the performance of the VCC system, a sample villa project was selected as a case study. The obtained results showed that EAHE system contributed efficiently to the COP of the VCC with an overall increase of 47 % and 49 % for R-22 and R410a cycles, respectively. Moreover, the calculated values were validated against Cycle_D simulation model and showed good agreement with a maximum deviation of 5%. The payback period for this project was found to be around two years while the expected life time is about 10 years which makes it an attractive investment.

Computational assessment of a full-scale Mediterranean building incorporating wallboards with phase change materials

2016 ◽  
Vol 26 (10) ◽  
pp. 1429-1443 ◽  
Author(s):  
Marianna E. Stamatiadou ◽  
Dimitrios I. Katsourinis ◽  
Maria A. Founti
Keyword(s):  
Phase Change ◽  
Phase Change Materials ◽  
Energy Savings ◽  
Cooling System ◽  
Residential Building ◽  
Energy Performance ◽  
Energy Potential ◽  
Two Phase ◽  
Change Temperature ◽  
Cooling Loads

In this study, a lightweight residential building in Greece was investigated, focusing on the summer comfort when wallboards with phase change materials (PCM) were installed in the external and internal walls. The effectiveness of the PCM wallboards installed was numerically assessed, while the energy performance of the building was examined, in order to quantify the effect of PCM in the annual cooling load needs, as a way of saving energy. Potential bigger energy savings were evaluated by defining the appropriate PCM melting temperature range and the ‘energy-conscious’ occupant behaviour (passive vs. active). Results were expressed in terms of percentage savings of cooling loads and with comparison to wall elements incorporated with plain gypsumboards instead of the PCM wallboards. The optimum phase change temperature change for the specific location was investigated by examining two-phase change transition temperatures of the PCM wallboards (PCM24 and PCM26 respectively). The use of PCM24 produced a 29% reduction of annual cooling loads, compared to 16% reduction produced by PCM26. Five scenarios were also examined, showing the behaviour of the PCM which was enhanced when a cooling system was installed. The cooling needs were lowered by an average of 25.7%, compared to the respective no-PCM scenarios.

scholarly journals Performance of Vapor Compression Refrigeration System using Nanoparticles – Based Mineral Oil Lubricant

2019 ◽  
Vol 8 (3) ◽  
pp. 730-734
Keyword(s):  
Electron Microscopy ◽  
Energy Savings ◽  
Size Structure ◽  
Mineral Oil ◽  
Coefficient Of Performance ◽  
Vapor Compression ◽  
Refrigeration System ◽  
X Ray Diffraction ◽  
Heat Transfer Efficiency ◽  
Transmission Electron

In general, mineral oil and polyester oil are used as lubricants in a refrigeration system compressor. The present work focuses mainly on the mineral oil based lubricant based on MWCNT nanoparticles. The different characterization of the multi-wall carbon nanotube (MWCNT) was performed using different methods such as Scanning Electron Microscopy (SEM), X-Ray Diffraction (XRD), and Transmission Electron Microscopy (TEM), which will result in size, structure and morphology of the CNT nanoparticle. First prepare the Nano-lubricants by adding nanoparticles in mineral oil with different concentrations of 0.05, 0.075 and 0.1wt% with the help of an ultrasonicator which will give the homogeneous mixture of Nanolubricant. Nanoparticles mixed with mineral oil used in a refrigeration system work safely and normally. The experiment were conducted on refrigeration system for different concentration, namely 0.05, 0.075 and 0.1wt% which will mixed with mineral oil and without nanoparticles in mineral oil. The result shows that 0.1wt% Nanolubricant which will give higher improvement in heat transfer efficiency and increase in the Coefficient of Performance (COP) by 37%. And energy savings is 9.6%.

scholarly journals Desiccant cooling as an alternative to traditional air conditioners in green cooling technology

2019 ◽  
pp. 01-13
Author(s):  
Jani DB
Keyword(s):  
Air Conditioning ◽  
Energy Savings ◽  
Cooling System ◽  
Green Building ◽  
Climatic Conditions ◽  
Coefficient Of Performance ◽  
Low Grade ◽  
Vapor Compression ◽  
Cooling Technology ◽  
Air Conditioning Systems

Desiccant-based dehumidification and air conditioning systems are considered as an energy efficient alternative to traditional vapor compression based air-conditioning systems for green building cooling technology especially in tropical hot and humid ambient climates. It is a novel green cooling technology that makes use of low-grade heat for building air conditioning. It is seen that the desiccant based dehumidification and cooling can efficiently provide comfort conditions in subtropical and especially hot and humid tropical climates. The desiccant integrated novel cooling system has a significant higher coefficient of performance compared to the conventional vapor compression system resulting to substantial electrical energy savings during the summer season by use of renewable solar energy, which also resulted in to major reduction in CO2 emissions. Therefore, these results demonstrate that there is a good potential in desiccant-based dehumidification and cooling system for energy and carbon savings while carry out building air-conditioning. Through a literature review, the feasibility of the desiccant assisted air conditioning in hot and humid climatic conditions is proven and the advantages it can offer in terms energy and cost savings are underscored. Keywords: Air-conditioning; Desiccant cooling; Dehumidification; Green cooling; Thermal comfort

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