scholarly journals Enhanced heat exchanger layout for optimum energy performance in solar thermal ORC-based unit

2019 ◽  
Author(s):  
Diego Vittorini ◽  
Roberto Cipollone ◽  
Roberto Carapellucci
Keyword(s):  
Heat Exchanger ◽  
Energy Performance ◽  
Solar Thermal ◽  
Optimum Energy

An Exergy-Based Metric for Evaluating Solar Thermal Absorber Technologies for Gas Heating

2011 ◽  
Author(s):  
Maritza Ruiz ◽  
Van P. Carey
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Loss Factor ◽  
Performance Metrics ◽  
Solar Thermal ◽  
Pumping Power ◽  
Central Receiver ◽  
Gas Heating ◽  
Goodness Factor ◽  
Solar Receiver

The energy conversion effectiveness of the central receiver absorber in concentrating solar thermal power systems is dictated primarily by heat losses, material temperature limits, and pumping power losses. To deliver concentrated solar energy to a gas for process heat applications or gas cycle power generation, there are a wide variety of compact heat exchanger finned surfaces that could be used to enhance the convective transfer of absorbed solar energy to the gas stream flowing through the absorber. In such circumstances, a key design objective for the absorber is to maximize the heat transfer thermodynamic performance while minimizing the pumping power necessary to drive the gas flow through the fin matrix. This paper explores the use of different performance metrics to quantify the combined heat transfer, thermodynamic and pressure loss effectiveness of enhanced fins surfaces used in solar thermal absorbers for gas heating. Previously defined heat exchanger performance metrics, such as the “goodness factor”, are considered, and we develop and explore the use of a new metric, the “loss factor”, for determining the preferred enhanced fin matrix surfaces for concentrated solar absorbers. The loss factor, defined as the normalized exergy loss in the receiver, can be used for nondimensional analysis of the desirable qualities in an optimized solar receiver design. In comparison to previous goodness factor methods, the loss factor metric has the advantage that it quantifies the trade-off between trying to maximize the solar exergy transferred to the gas (high heat transfer rate and delivery at high temperature) and minimizing the pumping exergy loss. In this study, the loss factor is used to compare current solar receiver designs, and designs that use a variety of available plate-finned compact heat transfer surfaces with known Colburn factor (j) and friction factor (f) characteristics. These examples demonstrate how the loss factor metric can be used to design and optimize novel solar central receiver systems, and they indicate fin matrix surfaces that are particularly attractive for this type of application.

On the Overall Energy Efficiency of a High-Performance Solar Energy Residential Building

2010 ◽  
Author(s):  
Adam J. Wong ◽  
Jorge E. Gonza´lez ◽  
Sergio Escobar ◽  
Mark Aschheim
Keyword(s):  
Solar Energy ◽  
High Performance ◽  
Residential Building ◽  
Weather Conditions ◽  
Energy Performance ◽  
Solar Thermal ◽  
Hvac System ◽  
Solar Pv ◽  
Solar Decathlon ◽  
Pv Array

This paper describes the energy performance of a solar house over its first year of monitoring. The 2007 Solar Decathlon house currently sits on Santa Clara University’s campus at 60.4 m2. The house is powered entirely by solar PV and solar thermal off the grid. This solar energy house is heavily instrumented with more than 100 sensors to measure temperatures, humidity, power consumption of electric appliances, lighting, water, and performance of a 7.2 kW solar PV array and a sophisticated HVAC system. The instrumentation includes a full weather station. The house is divided into two interconnected modules, and constructed with high thermal insulation and sustainable materials. The instrumentation also allows quantifying energy performance of individual components as well as the overall energy performance of the house. The paper focuses on the complete energy balance of the house as a function of weather conditions, and of the performance of individual components. Of particular interest is the performance of the solar PV and solar thermal systems. The solar thermal system includes an absorption air conditioning unit, integrated with a thermal storage tank to provide all energy needs for water consumption and heating. The I-V curves of the full PV array are reported, demonstrating peak, off-peak, and seasonal performance and deviations from manufacturers’ conditions. Similarly, the overall COP of the solar-driven HVAC system is reported for both cooling and heating modes. Finally, it is shown how data can be used to demonstrate improvement of simulation tools for solar building energy performance. Although data has been collected since March 2009, this paper focuses on performance during summer 2009.

Photovoltaic-Thermal Collector System for Domestic Application

Solar Energy ◽  
2005 ◽  
Author(s):  
T. T. Chow ◽  
J. Ji ◽  
W. He
Keyword(s):  
Energy Performance ◽  
Primary Energy ◽  
Heat Energy ◽  
Solar Thermal ◽  
Test Results ◽  
Thermal Systems ◽  
Collector System ◽  
Solar Thermal Collector ◽  
Reduced Temperature ◽  
Direct Attachment

Photovoltaic-thermal (PV/T) systems integrate photovoltaic and solar thermal technologies into one single system with dual production of electricity and heat energy. A typical arrangement is the direct attachment of PV modules on to a solar thermal collector surface. For a given collector surface area, the overall system energy performance is expected higher than the conventional “side-by-side” PV and solar thermal systems. In the development of PV/T collector technology using water as the coolant, the most common design follows the sheet-and-tube thermal absorber concept. Fin performance of the thermal absorber has been identified as one important factor that affects much the overall energy performance of the collector. Accordingly, an aluminum-alloy flat-box type PV/T collector prototype was constructed and tested. Our test results indicate that a high combined thermal and electrical efficiency can be achieved. The primary-energy-saving efficiency for daily exposure approaches 65% at zero reduced temperature operation. With a simple and handy design, the product is considered to be very suitable for domestic application.

THERMODYNAMIC ANALYSIS AND EXPERIMENTAL RESEARCH OF TRANSCRITICAL CO2 CYCLE WITH INTERNAL HEAT EXCHANGER AND DUAL EXPANSION

2013 ◽  
Vol 21 (01) ◽  
pp. 1350005 ◽  
Author(s):  
Z. WANG ◽  
Y. GONG ◽  
X. H. WU ◽  
W. H. ZHANG ◽  
Y. L. LU
Keyword(s):  
Heat Exchanger ◽  
Experimental Evaluation ◽  
Pressure Fluctuations ◽  
Internal Heat ◽  
Energy Performance ◽  
Evaporation Temperature ◽  
Internal Heat Exchanger ◽  
Side Pressure ◽  
Wide Range ◽  
Compressor Power

This work presents the experimental evaluation of the energy performance of transcritical CO2 refrigeration and heat pump systems. The optimal gas cooler pressures and the optimal COP have been analyzed from a thermodynamic point of view. The systems used a new dual expansion valve and a balance CO2 liquid receiver adjustment device, which can control high and low side pressure effectively. Moreover, we demonstrate the influence of the internal heat exchanger (IHX) on the systems' performances, on the basis of the analysis of the relative COP index RCOPI, the compressor power index RPCI and other parameters which can confirm the truth of. The experimental evaluation covers five evaporating levels (-10 to 10°C) and in a wide range of gas cooler pressures (75 to 120 bar). It is concluded that with the IHX system, compressor power is relatively low when the high side pressure is over 100 bar, and the evaporation temperature is below 0°C. The COP of the system without the IHX is slightly higher than the system with the IHX; it is increasing about 3% to 5%, when the evaporation temperature is over 5°C. Relative to the single expansion process, the dual expansion cycle can decrease the influence of pressure fluctuations of CO2 supercritical fluid and liquid mixture on the systems.

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