Dependence of Evaporation Temperature and Exergetic Efficiency of Air Split-Conditioners Heat Pumps from the External Air Temperature

2020 ◽  
pp. 253-259
Author(s):  
Volodymyr Labay ◽  
Vitaliy Yaroslav ◽  
Oleksandr Dovbush ◽  
Bohdan Piznak
Keyword(s):  
Air Temperature ◽  
Heat Pumps ◽  
Exergetic Efficiency ◽  
Evaporation Temperature

scholarly journals Mathematical modeling bringing the operation of air split conditioners heat pumps to the same internal temperature conditions

2021 ◽  
Vol 8 (3) ◽  
pp. 509-514
Author(s):  
V. Yo. Labay ◽  
◽  
V. Yu. Yaroslav ◽  
O. M. Dovbush ◽  
A. Ye. Tsizda ◽  
...  
Keyword(s):  
Air Temperature ◽  
Heat Pumps ◽  
Thermodynamic Efficiency ◽  
Condensation Temperature ◽  
Internal Temperature ◽  
Heating Systems ◽  
Evaporation Temperature ◽  
Temperature Conditions ◽  
Heating Capacity ◽  
The Mathematical Model

Nowadays, the use of heat pumps (HP) of air split-conditioners in air conditioning and heating systems of small industrial, public and residential facilities is becoming more common. It is known that the nominal heat capacity of HP of air split-conditioners is given in catalogs or reference literature under standard outdoor temperature conditions, namely: outdoor air temperature +7oС, indoor air temperature +21oС. At the same time, manufacturers of air split-conditioners do not ensure that, regardless of the size of heating capacity, all air split-conditioners have the same internal temperature conditions, namely: the evaporation temperature of the refrigerant and its condensation temperature. In this case, the thermodynamic efficiency, which can be best assessed by the exergetic output-input ratio (OIR) of different heating capacity of HP of air split-conditioners, is different; this, in our opinion, is incorrect. However, today there is a lack of mathematical models of bringing the operation of air split-conditioners HP to the similar internal temperature conditions, which will allow us to obtain the same exergetic OIR for different heating capacity of HP. To create the mathematical model of bringing the operation of HP of air split-conditioners to the equal internal temperature conditions, we have proposed them, namely: the evaporation temperature of the refrigerant +0.7oC and its condensation temperature +40oC. Taking these temperatures on the basis of the heat balances of the HP evaporator and HP condenser of air split-conditioners, we obtained the dependences for calculating air flow rates on the evaporator and condenser, which respectively maintain the proposed temperatures.

scholarly journals Exergetic and Economic Evaluation of a Transcritical Heat-Driven Compression Refrigeration System with CO2 as the Working Fluid under Hot Climatic Conditions

Entropy ◽  
2019 ◽  
Vol 21 (12) ◽  
pp. 1164 ◽  
Author(s):  
Jing Luo ◽  
Tatiana Morosuk ◽  
George Tsatsaronis ◽  
Bourhan Tashtoush
Keyword(s):  
Ambient Temperature ◽  
Climatic Conditions ◽  
Working Fluid ◽  
Refrigeration System ◽  
Exergetic Efficiency ◽  
Evaporation Temperature ◽  
Aspen Hysys ◽  
Operation Conditions ◽  
Heating Capacity ◽  
Refrigeration Machine

The purpose of this research is to evaluate a transcritical heat-driven compression refrigeration machine with CO2 as the working fluid from thermodynamic and economic viewpoints. Particular attention was paid to air-conditioning applications under hot climatic conditions. The system was simulated by Aspen HYSYS® (AspenTech, Bedford, MA, USA) and optimized by automation based on a genetic algorithm for achieving the highest exergetic efficiency. In the case of producing only refrigeration, the scenario with the ambient temperature of 35 °C and the evaporation temperature of 5 °C showed the best performance with 4.7% exergetic efficiency, while the exergetic efficiency can be improved to 22% by operating the system at the ambient temperature of 45 °C and the evaporation temperature of 5 °C if the available heating capacity within the gas cooler is utilized (cogeneration operation conditions). Besides, an economic analysis based on the total revenue requirement method was given in detail.

scholarly journals Comparative Energy and Exergy Analysis of a Thermal Power Plant With/Without Retrofitted Inlet Air Cooler: A Case Study

2018 ◽  
Vol 3 (6) ◽  
pp. 1
Author(s):  
Sufianu Adeiza Aliu ◽  
Promise Ijeoma Ochornma
Keyword(s):  
Power Plant ◽  
Energy Conversion ◽  
Gas Turbine ◽  
Air Temperature ◽  
Thermal Power ◽  
Second Law Of Thermodynamics ◽  
Second Law ◽  
Plant Analysis ◽  
Exergetic Efficiency ◽  
Air Cooler

The result of this study shows the performance of Ihovbor Gas Power Plant in Benin, Edo State Nigeria using first and second law of thermodynamics. Analysing the efficiency of the plant using first law of thermodynamics showed that with increase in inlet air temperature, the energy conversion efficiency of the plant reduces. The exergy efficiency of the plant also confirmed that increase in inlet air temperature results in decrease of the exergetic efficiency of the plant. Analysis of each of the components showed the greatest destruction of exergy was in the combustion chamber while the least is the Gas turbine section. Using numerical method in analyzing the gas turbine plant when retrofitting with an evaporative inlet air cooler showed better performance in energy conversion as power generation increased with an average of  1% per 1oC degree fall in temperature, the work ratio and thermal efficiency of the plant also increased. The analysis of the modified plant using second law of thermodynamics showed an increase in magnitude of both the exergy destroyed and the efficiency of the plant. Analysis showed that integrating evaporative cooler as component of the inlet air cooler increases the efficiency of the Air compressor by over 0.8%  thus increasing the plant’s exergetic efficiency.

Exergy Analysis of a Micro-Gas Turbine Fueled with Syngas

2013 ◽  
Vol 465-466 ◽  
pp. 142-148
Author(s):  
Hussain Sadig ◽  
Shaharin Anwar Sulaiman ◽  
Ibrahim Idris
Keyword(s):  
Combustion Chamber ◽  
Gas Turbine ◽  
Air Temperature ◽  
Heat Input ◽  
Ambient Air ◽  
Exergy Destruction ◽  
Exergetic Efficiency ◽  
Micro Gas Turbine ◽  
Ambient Air Temperature ◽  
Excess Air

A theoretical exergetic analysis of a small-scale gas-turbine system fueled with two different syngas fuels is discussed in this paper. For carrying out the analysis, a micro-gas turbine system with a thermal heat input of 50 kW was simulated using ASPEN plus simulator. Quantitative exergy balance was applied for each component in the cycle. The effects of excess air, ambient air temperature, and heat input on the exergy destruction and exergetic efficiency for each component were evaluated and compared with those resulted from fueling the system with liquefied petroleum gas (LPG). For 50 kW heat input and 50% excess air, the total exergy destruction for LPG, Syngas1, and Syngas2 were found to be 17.3, 14.3, and 13.6 kW, respectively. It was found that increasing the excess air ratio to 100% increased the combustion chamber exergetic efficiency by 8%-10% but it reduced the exergetic efficiency of other components. The same trend was observed when tested ambient air temperature. The results also showed a reduction in the combustion chamber exergetic efficiency by 2%-4% when a 20% heat input increase was applied.

scholarly journals ENERGY EFFICIENCY IN CONSTANTA HARBOR- A THEORETICAL ASSESSMENT OF THE PERFORMANCE OF A HEAT PUMP FOR HEATING NEEDS, FOR A LESS POLLUTANT ADMINISTRATION OFFICE

2021 ◽  
Vol 2021 (2) ◽  
pp. 33-38
Author(s):  
FEIZA MEMET
Keyword(s):  
Heat Pump ◽  
Air Temperature ◽  
Fossil Fuels ◽  
Heat Pumps ◽  
Coefficient Of Performance ◽  
Electrical Heating ◽  
Outdoor Air ◽  
Heated Water ◽  
Air Temperatures ◽  
Discharge Temperature

In accordance with the present energetic exigencies, the energy consumption in port buildings is of a vital importance. From this perspective, heat pumps are less pollutant and more energy efficient options than the traditional heating technologies. This study focuses on an air source heat pump (ASHP), operating in an administration office located in Constanta harbor, Romania, in order to supply heated water during December of 2020. Electrically driven heat pumps are seen as a successful alternative to classical expensive heating means, such as electrical heating or the one based on fossil fuels combustion. Within this research, are investigated influences of the heated water temperatures and exterior air temperatures on the theoretical Coefficient of Performance, the compression ratio and the discharge temperature. The cycle is working with R134a, with 50C superheating and sub cooling. It will be considered that the heated water is supplied in the range (40-50) 0C, while the outdoor air temperature varies in the range (0-10) 0C. Obtained results show that the highest efficiency of the ASHP is obtained for the lowest value of the heated water temperature and for the highest value of the outdoor air temperature. This situation corresponds also to the good working of the compressor of the refrigeration plant, since are seen lowest values of the compression rate and the discharge temperature, as well. This means that the compressor do not consume high amounts of energy and the oil is not damaged because of high temperatures of the refrigerant vapors.

Ground Air Temperature Control for Heat Pump Exchange. APTAE System

2021 ◽  
pp. 156-175
Author(s):  
David Palomar Aguilar ◽  
Carlos Miguel Iglesias Sanz ◽  
Sofia Corsini Fuhrmann
Keyword(s):  
Energy Consumption ◽  
Heat Exchange ◽  
Heat Pump ◽  
Air Temperature ◽  
Air Conditioning ◽  
Fossil Fuels ◽  
Heat Pumps ◽  
Thermal Exchange ◽  
Radon Gas ◽  
Heating And Cooling

Heating and cooling consume a high amount of energy, which is today mainly provided by fossil fuels. To save fossil resources and simultaneously reduce pollutants and CO2, heating and cooling energy consumption should be reduced. Geothermal energy is a clean, inexhaustible source of energy that is available all year round because it does not depend on the weather. Nevertheless, the use of tempered subsoil air has been used as a traditional air conditioning strategy; however, nowadays, its use has been questioned by the discovery of the leaks of radon gas from the ground. The investigation searches a heat exchange system with the subsoil which prevents the introduction of radon gas into living spaces. The system that is exposed increases the performance of aerothermal heat pumps by means of thermal exchange with tempered air in the sanitary chamber. This exchange is more favorable than air at the outside temperature, increasing the COP of the machine. This system complies with the regulations for protection against radon, protecting the building from this radioactive gas.

scholarly journals An analysis of effectiveness of air heat pump operation dependent on change of external air temperature

2021 ◽  
Vol 37 ◽  
pp. 24-30
Author(s):  
O. Shapoval ◽  
N.   Chepurna ◽  
M. Kirichenko
Keyword(s):  
Low Temperature ◽  
Water Temperature ◽  
Heat Pump ◽  
Air Temperature ◽  
Heat Carrier ◽  
Heat Pumps ◽  
Hot Water ◽  
Coefficient Of Performance ◽  
Outdoor Air ◽  
High Coefficient

Currently, air-to-water heat pumps are more widely used, which due to the high coefficient of performance reduce energy consumption and negative impact on the environment. They decrease the dependency on costs of energy resources. The work is devoted to solving the urgent problem of improving the efficiency of air heat pumps at low temperature of outdoor air in winter. One of the main problems of an air heat pump is the reduction of productivity when the outdoor air temperature decreases in winter. In this paper, the effectiveness of LG Therma V air-to-water heat pump to provide apartments with heating and hot water supply was analyzed. The heat pump is reversive, which can cool or heat a heat carrier. A four-way valve swithes the coolant flows between air exchangers. On the basis of the obtained results, plots of effectivness of the heat pump dependent on outdoor air temperature are built. It is shown that the effectiveness of the heat pump significantly depends not only on the outside temperature but also on the water temperature at the outlet of the heat pump. The use of heat pumps with a high coefficient of performance can significantly reduce energy costs. The most effective are low-temperature heating systems, in which the water temperature does not exceed 45 °C. The example is floor heating, which requires very low temperature of the floor surface – up to 30 °C. At outdoor air temperature not less than milnus 7 °C the heat pump is effective at higher temperature off heat carrier at output – up to 55 °C. To provide the uninterrupted heat supply, an additional air heater is included. It covers heat load during defrosting and very low outdoor air temperature. On the basis of the conducted researches, the directions of the further experimental and field researches are planned.

scholarly journals Simulation analysis and optimization research on cooling and dehumidifying effects for evaporator

2020 ◽  
pp. 167-167
Author(s):  
Shuailing Liu ◽  
Guoyuan Ma ◽  
Shuxue Xu ◽  
Fuping Li ◽  
Chenzhe Hang
Keyword(s):  
Wind Speed ◽  
Relative Humidity ◽  
Moisture Content ◽  
Linear Relationship ◽  
Air Temperature ◽  
Simulation Analysis ◽  
Evaporation Temperature ◽  
Temperature And Humidity ◽  
The Difference

The improvement performance of refrigerating dehumidification system was theoretically discusses based on a dehumidification model. The influence of evaporator inlet wind speed, dry bulb temperature and relative humidity on dehumidification were analysed by the model. The results show that, when inlet air temperature and humidity were kept constant, the dehumidification capacity increased first and then decreased with increase of the wind speed; When the moisture content and the wind speed of the inlet air were kept constant, the dehumidification capacity gradually decreased with increase of the inlet air dry bulb temperature; The inlet air dry bulb temperature was between 21-36 ?C and the relative humidity was between 40% and 85%, the difference between the inlet air wet bulb temperature and the evaporation temperature at the optimum COP was about 10 ?C; There was a nearly linear relationship between the corresponding evaporation temperature at the optimal COP and the evaporation temperature with the maximum dehumidification capacity, compared with the test value, the error was less than 10%.

scholarly journals STUDY OF THE DISTRIBUTION OF AIR TEMPERATURE IN A GREENHOUSE HEATED BY AIR TO AIR HEAT PUMP

2021 ◽  
Vol 1 ◽  
pp. 17-22
Author(s):  
Agris Auce ◽  
Aivars Jermuss ◽  
Adolfs Rucins ◽  
Semjons Ivanovs ◽  
Ugis Grinbergs
Keyword(s):  
Temperature Distribution ◽  
Heat Pump ◽  
Air Temperature ◽  
Temperature Stability ◽  
Control Unit ◽  
Temperature Sensors ◽  
Heat Pumps ◽  
Industrial Facility ◽  
Tomato Plants ◽  
Gas Heating

The temperature distribution inside the experimental greenhouse heated by air to air heat pumps and its impact on the growth and productivity of tomato plants were studied. Experimental greenhouse located at SIA Rītausma facility in South-East Latvia.Two commercially available regular air to air heat‑pumps with a combined heat power of 10 kW were used. To measure the temperature distribution, 18 temperature sensors with solar radiation shields at different heights and positions among the plants were installed. Additional 4 temperature sensors were used to measure the air flow temperature at the heating elements. Reference air temperature was measured at an industrial production facility heated by a common gas heating system.Temperature was found to be homogenous within 1 °C. Observed temperatures were up to 4 °C lower than set on the control unit of the heat pump. This discrepancy was compensated by higher set values for the controlling unit. As research showed the temperature stability was better than at the water-heated industrial facility at time slots when the sun was suddenly cleared from clouds.The cooling of the experimental greenhouse by air conditioning during summer time was rather challenging for the tomato plants and productivity. 23% of plant stems died until the end of the season and the yield was 50% lower than in the reference greenhouse. The energy efficiency compared to the industrial facility was approx. 8 times better and the estimated CO2 emissions were 8-16 times smaller compared to gas heating. There were no increases of heating costs determined.Further studies are needed to optimize the heating parameters and reach the desired greenhouse productivity. 

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