Energy-Efficient Air-Conditioning Systems for Nonhuman Applications

In addition to humans’ thermal comfort, air-conditioning (AC) could be required for various nonhuman applications, for example, animals’ AC, greenhouse AC, food storage and transportation, industrial processes, and so on. In this regard, optimum conditions of air temperature and humidity are explored and compared on psychrometric charts. Thermodynamic limitations of existing AC systems are discussed from the subject point of view. Consequently, four kinds of low-cost energy-efficient AC systems, namely: (i) direct evaporative cooling (DEC), (ii) indirect evaporative cooling (IEC), (iii) Maisotsenko cycle (M-Cycle) evaporative cooling (MEC), and (iv) desiccant AC (DAC), are investigated for climatic conditions of two cities, that is, Multan (Pakistan) and Fukuoka (Japan). In addition, systems’ fundamentals and principles are explained by means of schematic diagrams and basic heat/mass transfer relationships. According to the results, performance of all systems is influenced by ambient air conditions; therefore, a particular AC system cannot provide optimum AC for all nonhuman applications. However, one or other AC system can successfully provide desired conditions of temperature and relative humidity. It has been concluded that evaporative cooling systems provide low-cost AC for dry climates, whereas DAC system is found energy efficient and viable for humid climates

Investigation of Desiccant and Evaporative Cooling Systems for Animal Air-Conditioning

Productivity of livestock animals particularly sheep, goats, dairy, and beef cattle are usually affected due to high thermal/heat (sensible and latent) stresses, particularly in the developing countries. Different types of heating, ventilation, and air-conditioning (HVAC) systems are used worldwide depending upon the ambient air conditions to achieve the animals’ thermal comfort. In this chapter, few low-cost options for the air-conditioning system and for farm building designs are discussed. Desiccant-based two air-conditioning systems are considered i.e., standalone desiccant air-conditioning (D-AC) and M-cycle assisted D-AC (M-DAC) system. The feasibility of both systems is thermodynamically checked for climatic conditions of Multan, Pakistan. Daily- basis data of ambient and processed air from both systems are analyzed for the thermal comfort of Holstein Friesian cows. Temperature humidity index (THI) is calculated to investigate the thermal heat stress conditions. Results showed that the D-AC system can be used efficiently in the humid climatic conditions with relatively moderate-to-low temperatures. On the other hand, the M-DAC system can be used in humid climatic conditions with relatively high-temperature conditions. It is important to mention that the typical direct evaporative cooling systems can be obviously low-cost options in case of dry climatic conditions

Experimental Investigation of Relative Humidity Effect on the Thermal Conductivity of Desiccant Material

Study on effective thermal conductivity (ETC) of desiccant materials is getting attention in the literature in order to optimize the operating parameters of close and open cycle adsorption cooling systems. In addition, it is an important parameter to enhance the performance of adsorption heat pump and adsorption cooling systems (AHP/ACS). Most of the desiccant materials are porous in nature, therefore, results in different ETC at different operating conditions i.e. temperature and humidity. In order to find the more precise performance expression, the combined effect of desiccant porosity, temperature and relative humidity (RH) should be considered. In this regard, many empirical and theoretical models have been presented for the estimation of ETC. Models developed in the literature are characterized by a single value at a particular temperature irrespective of humidity. Hence this study experimentally investigates the relative humidity effect on the thermal conductivity of the commercially available desiccant material i.e. AQSOA-Z05.The levels of RH were investigated in the range of 8% to 100%. The results showed that ETC of oven dry adsorbent material was 0.066 W/mK whereas it increased from 0.067-0.089 W/mK at RH of 8-100%, respectively. The ETC values increase due to the phenomena of pores filling by water vapor adsorption. It also showed that pore filling incorporate the change in the mean free path and it varied from 6.93-0.55μm at RH range 8-100%, respectively. Consequently, an empirical correlation has been presented which can predict the effective thermal conductivity at different levels of RH

Techno-economic analysis on the balance of plant (BOP) equipment due to switching fuel from natural gas to hydrogen in gas turbine power plants

The concerns over greenhouse gas emissions, environmental impacts, climate change, and sustainability continue to grow. As a result of countermeasures, many modern gas turbine power plants and combined cycle power plants are considering to use hydrogen as a clean fuel alternative to fossil fuels in the power plant industry. We assessed the implications of such transition from natural gas to hydrogen as fuel in a gas turbine power plant's balance of plant (BOP) equipment. Using the DWSIM process simulation software and the methodology of compression power changes against different gas compositions, the impact of blending hydrogen with natural gas on temperature differentials, energy consumption, adiabatic efficiency, compression power, and economic implications in gas turbine power plants were examined in this paper. We discovered, through analysis, that there was not a noticeable boost in compression power or energy consumption when 50% hydrogen and 50% natural gas were blended. Similarly, there was no discernible difference in temperature differentials or adiabatic efficiency when 30% hydrogen and 70% natural gas were blended. Moreover, mixing 50% hydrogen and 50% natural gas did not result in a noticeable cost climb. In addition, the techno-economic analysis presented in this paper offered valuable insights for power plant engineers, power generation companies, investors in energy sectors, and policymakers, highlighting the nature of the fuel shift and its implications on the economy and technology

Theoretical and Experimental Analysis of Desiccant Air Conditioning System for Storage of Agricultural Products

The study emphasizes on the use of desiccant air conditioning (DAC) system for the storage of agricultural products. The chilling sensitivity of the tropical fruits and vegetables makes this system more promising for their optimal storage. The desiccant air conditioning system assisted by Maisotsenko cycle evaporative cooler is proposed in the study to achieve the latent and sensible load of air conditioning. In this regard, the dehumidification evaluation of the honeycomb like polymer based hydrophilic desiccant blocks are carried out by the means of an open-cycle experimental unit. The representative ideal storage zones of three temperature and relative humidity compatible groups of fruits and vegetables are established on the psychrometric chart on the basis of published data. The ideal DAC cycle analysis is accomplished at low regeneration temperature (55°C) for case-I (T = 31°C; RH = 21%) and case-II (T = 13°C; RH = 70%). The dehumidification analysis of the desiccant blocks recommended the time ratio between regeneration and dehumidification modes as 1:1 and 2:3 for the case-I and case-II respectively. The suggested time ratios ensure the dehumidification of the process air up to 2 g/kg of dry air and 4 g/kg of dry air in case-I and case-II respectively. The COP of the system was calculated as 0.90-0.43 and 0.55-0.25 at 30-90 minutes dehumidification with regeneration heat supplies of 1.7-2.3 kW and 2.5-3.5 kW in case-I and case-II respectively. The promising dehumidification by the desiccant blocks resulted in achieving the latent load itself followed by flat plate heat exchanger and Maisotsenko cycle evaporative cooler to achieve the sensible load. However, in case of high sensible loads hybrid DAC system is being recommended in this study

Performance Evaluation of Heat Pump Cycle using Low GWP Refrigerant Mixtures of HFC-32 and HFO-1123

Hydro-fluorocarbons (HFCs) have been widely used as working fluids (refrigerants) in air-conditioning and refrigeration systems. At the 1997 Kyoto Conference (COP3), a worldwide agreement was obtained to regulate the production and use of HFCs exhibit high global warming potential (GWP). In the above situation, Hydro-fluoro Olefins (HFOs) having extremely low GWP values such as HFO-1234yf, HFO-1234ze(E), HFO-1123, has attracted attentions. In this study, the performance of heat pump cycle using low GWP refrigerant mixtures of HFC-32 and HFO-1123 is evaluated experimentally. The experimental system is a water heat source vapor compression cycle, mainly composed of an inverter-controlled & hermetic-type scroll compressor (cylinder volume: 11 cm3), an oil separator, a double-tube-type condenser (heat transfer tube; inner grooved , OD 9.53 mm, ID 7.53 mm, total length 7.2 m), a liquid receiver, a solenoid expansion valve, and a double-tube-type evaporator (heat transfer tube; inner grooved , OD 9.53 mm, ID 7.53 mm, total length 7.2 m). Tested compositions of mixtures of HFO-32/HFO-1123 are 58/42 mass% (GWP=393) and 42/58 mass% (GWP=285). These mixtures are tested for the heating and the cooling modes. In the heating mode, the heat sink water temperatures at the inlet and outlet of condenser are kept at 20 ˚C and 45 ˚C, respectively, and the heat source water temperatures at the inlet and outlet of evaporator are kept at 15 ˚C and 9 ˚C. Then, the heating load is varied from 1.6 kW to 2.6 kW. Similarly, in the cooling mode, the water temperature at the inlet and outlet are kept at 30 ˚C and 45 ˚C in condenser, and at 20 ˚C and 10 ˚C in evaporator. Then, the cooling load is varied from 1.4 kW to 2.4 kW. The conventional refrigerant R410A is also tested as the reference. In both modes of heating and cooling, the COP of HFO-32/HFO-1123 mixture (58/42 mass%) is almost the same as that of R410A, while the COP of HFO-32/HFO-1123 mixture (42/58 mass%) is a little lower than that of R410A. By analyzing the irreversible loss of the heat pump cycle based on the second low analysis, the losses of both mixtures in condenser and evaporator are slightly smaller than that of R410A, while the losses of both mixtures in compressor are slightly higher than that of R410A. This result reveals that tested mixtures of HFO-32/HFO-1123 are available to use as the alternative of R410A if the design of compressor and heat exchangers are optimized

Optimized Performance of One-Bed Adsorption Cooling System

Adsorption cooling system can be driven by solar energy or waste heat, so it will effectively reduce fossil fuel consumptions when total system is well-designed. On the other hand, the system tends to have a large size, which will be an obstacle to install adsorption cooling systems to small to medium scale cooling demands, such as automobiles, houses, or shops. The study was aiming at the reduction of system size of adsorption cooling systems for refrigeration and air-conditioning applications. To simplify the system, we investigated one-bed configuration of adsorption cooling system. In general, one-bed adsorption cooling system would result in a large temperature fluctuation at chilled water outlet. To overcome that drawback and to maximize the cooling capacity, the cycle time, namely, pre-heating, desorption, pre-cooling, and adsorption times, of one-bed adsorption cooling system was optimized. In case of two-bed adsorption cooling system, two adsorbers operates in reverse phase each other, which means that the degree of freedom for cycle time optimization is two. In case of one-bed adsorption cooling sytem, four processes can be independently optimized. In our study, activated carbon-ethanol pair was chosen as the adsorbent-refrigerant pair because of a high adsorption capacity of activated carbons against ethanol. Using adsorption isotherms and kinetic data of activated carbon-ethanol pair measured by our research group, a lumped parameter model of one-bed adsorption cooling system was developed. The four parameters of cycle time were optimized using global optimization method, and the optimal time settings were effectively found. The results showed the effect of cycle time optimization on the cooling performance of one-bed adsorption cooling system