scholarly journals Effects of Ambient Parameters on the Performance of a Direct-Expansion Solar-Assisted Heat Pump with Bare Plate Evaporators for Space Heating

2017 ◽  
Vol 2017 ◽  
pp. 1-10 ◽  
Author(s):  
Wenzhu Huang ◽  
Jie Ji ◽  
Mawufemo Modjinou ◽  
Jing Qin
Keyword(s):  
Relative Humidity ◽  
Ambient Temperature ◽  
Heat Pump ◽  
Solar Irradiance ◽  
Solar Irradiation ◽  
Space Heating ◽  
Direct Expansion ◽  
Ambient Conditions ◽  
Solar Simulator ◽  
Independent Effects

Research on the direct-expansion solar-assisted heat pump (DX-SAHP) system with bare plate evaporators for space heating is meaningful but insufficient. In this paper, experiments on a DX-SAHP system applying bare plate evaporators for space heating are conducted in the enthalpy difference lab with a solar simulator, with the ambient conditions stable. The independent effects of ambient temperature, solar irradiation, and relative humidity on the system performance are investigated. When ambient temperature changes as 5°C, 10°C, and 15°C, COP increases as 2.12, 2.18, and 2.26. When solar irradiance changes as 0 W m−2, 100 W m−2, 200 W m−2, 300 W m−2, and 500 W m−2, COP of the system changes as 2.07, 2.09, 2.14, 2.26, and 2.36. With ambient temperature of 5°C and solar irradiance of 0 W m−2, when relative humidity is 50%, no frost formed. Whereas with relative humidity of 70% and 90%, frost formed but not seriously frosted after 120 min of operating. Frost did not deteriorate but improved the heating performance of the DX-SAHP system. The change of relative humidity from 70% to 90% improves the evaporating heat exchange rate by 35.0% and increases COP by 16.3%, from 1.78 to 2.07.

scholarly journals Experimental Study of a Novel Direct-Expansion Variable Frequency Finned Solar/Air-Assisted Heat Pump Water Heater

2018 ◽  
Vol 2018 ◽  
pp. 1-11 ◽  
Author(s):  
Jing Qin ◽  
Jie Ji ◽  
Wenzhu Huang ◽  
Hong Qin ◽  
Mawufemo Modjinou ◽  
...  
Keyword(s):  
Energy Consumption ◽  
Ambient Temperature ◽  
Heat Pump ◽  
Operating Mode ◽  
Heating Time ◽  
Solar Irradiation ◽  
Variable Frequency ◽  
Direct Expansion ◽  
Water Heater ◽  
Heat Pump Water Heater

A novel direct expansion variable frequency finned solar/air-assisted heat pump water heater was fabricated and tested in the enthalpy difference lab with a solar simulator. A solar/air source evaporator-collector with an automatic lifting glass cover plate was installed on the system. The system could be operated in three modes, namely, air, solar, and dual modes. The effects of the ambient temperature, solar irradiation, compressor frequency, and operating mode on the performance of this system were studied in this paper. The experimental results show that the ambient temperature, solar irradiation, and operating mode almost have no effect on the energy consumption of the compressor. When the ambient temperature and the solar irradiation were increased, the COP was found to increase with decreasing heating time. Also, when the compressor frequency was increased, an increase in the energy consumption of the compressor and the heat gain of the evaporator were noted with a decrease in the heating time.

Combined Solar Heating and Cooling Systems: Simulation and Design Optimization

2008 ◽  
Author(s):  
Giovanni Nurzia ◽  
Giuseppe Franchini ◽  
Antonio Perdichizzi
Keyword(s):  
Design Optimization ◽  
Heat Pump ◽  
Solar Heating ◽  
Solar Irradiation ◽  
Space Heating ◽  
Thermal Source ◽  
Absorption Chiller ◽  
Cooling Systems ◽  
Detailed Model ◽  
Heating And Cooling

The deployment of solar driven air conditioning is a feasible target in all countries where high solar irradiation matches high cooling loads in buildings: the goal is to gradually replace compression chillers and reduce peak electricity demand during summer. Moreover, as solar thermal collectors are installed, solar cooling systems can be profitably employed during winter. In the present work a code has been implemented for the simulation and the design optimization of combined solar heating and cooling systems. The following system layout has been considered: in warm months the cooling demand is satisfied by means of an absorption chiller — driven by a solar collector field — and a reversible heat pump operating in series. A hot storage matches the variability of solar radiation, while a cold storage smoothes the non-stationarity of cooling demand. During winter, the reversible compression heat pump operates for space heating. Solar collectors are used as thermal source at the evaporator of the heat pump, increasing its coefficient of performance. The code, based on TRNSYS platform, is able to simulate the system throughout a year. Besides TRNSYS standard components a detailed model of the absorption chiller has been included, in order to accurately simulate its off-design operation. Using an optimization tool the size of each component is identified for a given space heating and cooling demand. The minimization of life cycle costs of the system has been chosen as the objective of the optimization. Results of a case study are presented and discussed for a solar heating and cooling plant in an office building. The optimization procedure has been carried out with simulations for a typical Northern Italy town (Alpine climate) and a typical Southern Italy town (Mediterranean climate).

598 Temperature profiles of sunlight-exposed surfaces in a desert climate: Determining the risks for pavement burns.

2021 ◽  
Vol 42 (Supplement_1) ◽  
pp. S150-S151
Author(s):  
Paul J Chestovich ◽  
Richard Z Saroukhanoff ◽  
Syed F Saquib ◽  
Joseph T Carroll ◽  
Carmen E Flores ◽  
...  
Keyword(s):  
Ambient Temperature ◽  
Solar Irradiance ◽  
Time Of Day ◽  
Temperature Measurements ◽  
Solar Irradiation ◽  
Porous Rock ◽  
Solid Materials ◽  
Contour Plots ◽  
Desert Climate ◽  
Sunlight Intensity

Abstract Introduction In the desert climates of the United States, plentiful sunlight and high summer temperatures cause significant burn injuries from hot pavement and other surfaces. Although it is well known that surfaces reach temperatures sufficient to cause full-thickness burns, the peak temperature, time of day, and highest risk materials is not well described. This work measured continuous temperature measurements of six materials in a desert climate over a five-month period. Methods Six different solid materials common in an urban environment were utilized for measurement. Asphalt, brick, concrete, sand, porous rock, and galvanized metal were equipped with thermocouples attached to a data acquisition module. All solid materials except metal were placed in a 2’x2’x3.5” form, and identical samples were placed in both shade and direct sunlight. Ambient temperature was recorded, and sunlight intensity was measured using a pyranometer. Measurement time interval was set at three minutes. A computational fluid dynamics (CFD) model was created using Star CCM+ to validate the data. Contour plots of temperature, solar irradiance, and time of day were created using MiniTab for all surfaces tested. Results 75,000 temperature measurements were obtained from March through August 2020. Maximum recorded temperatures for sunlight-exposed samples of porous rock was 170 F, asphalt 166 F, brick 152 F, concrete 144 F, metal 144 F, and sand 143 F. Peak temperatures were recorded on August 6, 2020 at 2:10 pm, when ambient temperature was 120 F and sunlight intensity 940 W/m2 (Table). Temperatures ranged from 36 F - 56 F higher than identical materials in the shade at the same time. The highest daily temperatures were achieved between 2:00 pm to 4:00 pm due to maximum solar irradiance. Contour plots of surface temperature as function of solar irradiation and time of day were created for all surfaces tested. Nearly identical results obtained from the CFD models to the experimentally collected data, which validated the experimental data. Conclusions Surfaces exposed to direct, continuous sunlight in a desert climate achieve temperatures from 143 F to 170 F in the early afternoon and are high enough to cause significant injury with sufficient exposure. Porous rock reached the highest temperature, followed closely by asphalt. This information is useful to inform the public of the dangers of exposed surfaces in a desert climate.

scholarly journals Characterization Performance of Monocrystalline Silicon Photovoltaic Module Using Experimentally Measured Data

2019 ◽  
Vol 25 (10) ◽  
pp. 1-19
Author(s):  
Mena Safaa Mohammed ◽  
Emad Talib Hashim
Keyword(s):  
Ambient Temperature ◽  
Solar Irradiance ◽  
Clean Energy ◽  
Monocrystalline Silicon ◽  
Solar Irradiation ◽  
Weather Data ◽  
Photovoltaic Module ◽  
Solar Pv ◽  
Solar Module ◽  
Pv Module

Solar photovoltaic (PV) system has emerged as one of the most promising technology to generate clean energy. In this work, the performance of monocrystalline silicon photovoltaic module is studied through observing the effect of necessary parameters: solar irradiation and ambient temperature. The single diode model with series resistors is selected to find the characterization of current-voltage (I-V) and power-voltage (P-V) curves by determining the values of five parameters ( ). This model shows a high accuracy in modeling the solar PV module under various weather conditions. The modeling is simulated via using MATLAB/Simulink software. The performance of the selected solar PV module is tested experimentally for different weather data (solar irradiance and ambient temperature) that is gathered from October 2017 to April 2018 in the city of Baghdad. The collected data is recorded for the entire months during the time which is limited between 8:00 AM and 1:00 PM. This work demonstrates that the change in a cell temperature is directly proportional with the PV module current, while it is inversely proportional with the PV module voltage. Additionally, the output power of a PV module increases with decreasing the solar module temperature. Furthermore, the Simulink block diagram is used to evaluate the influence of weather factors on the PV module temperature by connecting to the MATLAB code. The best value from the results of this work was in March when the solar irradiance was equal to 1000 W/m2 and the results were: Isc,exp=3.015, Isc,mod=3.25 , RE=7.79 and Voc,exp=19.67 ,Voc,mod=19.9 ,RE=1.1

Rotary Compressor Performance at Low Ambient Temperatures

2020 ◽  
Vol 28 (04) ◽  
pp. 2050037
Author(s):  
S. Lowrey ◽  
G. Reboux
Keyword(s):  
Ambient Temperature ◽  
Heat Loss ◽  
Heat Pump ◽  
Simulated Data ◽  
Performance Testing ◽  
Rotary Compressor ◽  
Ambient Conditions ◽  
Ambient Temperatures ◽  
Compressor Performance ◽  
Performance Envelope

Small rotary compressors are used in domestic heat pump appliances, for example, in domestic dehumidifiers and heat pump clothes dryers. Compressor performance curves provided by the manufacturer can be based on testing at relatively high ambient temperatures, in some cases as high as 35∘C. This can be much higher compared with the ambient temperature in which the compressor operates when, for example, it is installed in a domestic dehumidifier which can operate in ambient temperatures as low as 10∘C. We have developed a compressor calorimeter to test a small R134a rotary compressor extracted from a commercial domestic dehumidifier and use this to measure compressor performance parameters including the isentropic and volumetric efficiencies and the compressor heat loss fraction. The performance testing has been carried out at ambient temperatures 10∘C, 15∘C, 20∘C and 25∘C for a fixed relative humidity of 70% to compare how the compressor performance varies with the ambient temperature, and to determine how well the compressor performs outside of the performance envelope provided by the manufacturer. The results show that isentropic and volumetric efficiency of these small compressors is relatively insensitive to variation in ambient temperature, even outside of the performance envelope provided by the manufacturer. However, the compressor heat loss fraction can, on average, double from 15% to 30%, between operation at ambient 25∘C and ambient 10∘C. The data obtained in this work is used to construct compressor sub-models for certain ambient temperatures. We show how these sub-models can be used to improve a domestic dehumidifier model for operation at low ambient conditions within the evaporator frosting regime and good agreement is obtained between experimental and simulated data. The authors are not aware of a domestic dehumidifier model designed to work at ambient temperatures within the frosting regime.

scholarly journals Thermodynamic analysis of a direct expansion solar assisted heat pump water heater

2017 ◽  
Vol 26 (2) ◽  
pp. 110 ◽  
Author(s):  
Masoud Yousefi ◽  
Misagh Moradali
Keyword(s):  
Ambient Temperature ◽  
Heat Pump ◽  
Coefficient Of Performance ◽  
Water Tank ◽  
Direct Expansion ◽  
Water Heater ◽  
Domestic Water ◽  
Heat Pump Water Heater ◽  
Thermodynamic Performance ◽  
Flat Plate Solar Collector

In this paper, the thermodynamic performance of a direct expansion solar assisted heat pump (DX-SAHP), which is used to heat domestic water from 20˚C to 45˚C, is theoretically investigated. The system includes a 3m2 single-cover flat plate solar collector, 0.150m3 water tank and 70m tube immersed in the water tank as a condenser. The effect of various parameters such as radiation on the collector surface, compressor speed and the ambient temperature on the coefficient of performance (COP) are calculated. Results show that obtained COP is considerably more than that of a conventional heat pump water heater when radiation on the collector is high. Also, increasing collector area and reducing compressor speed enhance COP. The same occurs when the ambient temperature increases. For instance, at an ambient temperature of 15˚C and 450 w/m2 irradiation on collector surface, the calculated COP was 6.37.

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