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The main purpose of this research is to suggest a virtual water flowmeter applicable in hydraulic systems with low-cost sensors. Practical procedures for realizing virtual water flowmeters for constant flow pumps (i.e., Cases 1 and 2) and variable flow pumps (i.e., Cases 3 and 4) are proposed in this paper. In Case 1, for measuring the water flow rate through a constant flow pump, the pump head was measured and the water flow rate was estimated using the pump characteristic curve obtained from the manufacturer or by deriving an empirical model based on the field measurement data. In Case 2, the water flow rate through a valve with a constant flow pump was estimated by measuring the pressure head between the valve and the valve opening position. The valve characteristic curve can be obtained by deriving an empirical model based on the initial field test results. The water flow rate through the variable flow pump was calculated, using the pump affinity laws and an empirical model, by measuring the frequency (i.e., Case 3) or input power (i.e., Case 4). The initial setup and test procedures for virtual flowmeters are also proposed in this research for practical use in the field. To verify the proposed procedures, experiments were conducted using constant and variable flow pumps in a pilot system. It was found that the virtual water flowmeters showed 2.9% to 6.7% of root mean square error from Case 1 to Case 4, compared with an ultrasonic water flowmeter, through long-term experimental verification.

The main purpose of this research was to experimentally investigate a liquid desiccant and evaporative cooling-assisted 100% outdoor air system. The proposed system was integrated with water-side free cooling in the desiccant solution and process air cooling to enhance its energy performance. The experimental results show that the required cooling water temperature for the desiccant solution is higher than the conventional cooling water supply temperature; that is, approximately 22–27 °C. Consequently, water-side free cooling was applied to produce the cooling water for the desiccant solution. The operation of the proposed system with the water-side economizer showed a 40–70% effectiveness of the indirect evaporative cooler, while that of the direct evaporative cooler was greater than 95%, and the supply air temperature ranged between 17 and 20 °C. The energy coefficient of performance (COP) of water-side free cooling applied to cool the desiccant solution was 8–17, whereas that of the conventional air-cooled chiller was 1–3. Economic consideration indicated that the operating energy savings might offset the penalty in the initial cost of the proposed system.

This paper proposes a server model that can be applied to simulating the annual cooling energy consumption of data centers and an analysis of its impact. Recently, aisle containment architecture and the variable air volume system have been widely adopted in the data center industry because of their superior indoor thermal management and cooling energy savings. However, the current simulation method, which fixes the server heat generation and the supply and return air temperature difference of the computer room air handler (CRAH), does not correctly reflect current cooling systems. In this study, a server model was developed that accounts for server thermal characteristics – including server power, fan airflow, and exhaust temperature – according to the given CPU utilization and temperature. After the proposed server model was validated, the annual cooling energy consumption was simulated for modular data centers with an air-side economizer and high ambient temperature. Unlike the conventional method, the proposed model showed that the cooling energy consumption increased when the CRAH supply air temperature was higher than 19 °C because of the increase in fan energy consumption.

a b s t r a c t The purpose of this research is to investigate the annual operating energy performance of a desiccant and evaporative-cooling-assisted 100% outdoor air system. The seasonal mode of operation of the proposed system is also suggested and used for estimating the energy saving potentials. The TRNSYS 16 program integrated with a commercial equation solver is used for the energy simulation of the proposed system, and then two existing air handling alternatives: a conventional variable air volume (VAV) system and an existing evaporative-cooling-assisted system are compared with the proposed system. The proposed system shows operating energy savings of 82% over the conventional VAV system dur- ing the summer, and 54% and 37% in the winter and the intermediate season operations, respectively. Ultimately, the proposed system provides 68% annual operating energy saving over the conventional VAV system, and 23% savings compared to the established evaporative-cooling-assisted system. It is also found that the extreme energy benefit can be obtained by enhancing the evaporative cooling effects using the liquid desiccant (LD) unit. The operating energy saving of the LD unit can be achieved by applying the water-side free cooling and the solar thermal system. © 2014 Elsevier B.V. All rights reserved.

An air-handler fan pressurization method can be used to estimate envelope leakage in large or tall buildings. However, because the size of a building's air handling system is designed only to meet heating and cooling demands, there may be many unanticipated problems on the test site. For example, one may not be able to perform the envelope leakage test using the air-handler fan(s) with relatively high pressure differences across the building envelope (e.g. 50–75 Pa). In order to overcome the insufficient pressurization problem faced during the air handler fan pressurization test, a combination of an air-handler and a blower door is proposed and verified by performing a pressurization test in an office building. It was found that the proposed method is feasible for evaluating the overall envelope leakage in large or tall buildings.

In this study, a hybrid ventilation system was proposed to reduce indoor heating and cooling loads owing to ventilation by using the heat storage and discharge effects of some heat storage materials. A pilot system of the ventilating system, comprised of heat storage material, a filter, as well as supply and exhaust fans, was also built. To measure the energy saving performance of the system, the following quantitative indicators were used: heat storage time, heat discharge time, heat storage material efficiency and reduction of ventilation loads. These indicators were measured based on actual data gathered from four test operations. The result shows that polycarbonate-based heat storage material has a longer heat discharge time compared to heat storage time, and a reduced ventilation heating load by over 37%.

The main thrust of this research is to verify the heating energy reduction capacity of an indirect and direct evaporative cooler assisted 100% outdoor air system (IDECOAS) via actual winter operation of the pilot unit installed in a campus building. A conventional variable air volume (VAV) system was also installed for comparison with the proposed system. By measuring variation of air temperature and relative humidity at each measurement location, effectiveness values of the indirect evaporative cooler (IEC) and the sensible heat exchanger (SHE) were monitored. In addition, the influence of balanced and unbalanced flow conditions between the supply air and the exhaust air on the sensible heat exchange effectiveness was also observed. Fan energy and heating coil energy consumptions were also measured by installing a wattmeter at each device. It was concluded that the IDECOAS shows 60–85% operating energy saving over the conventional VAV system. The sensible heat reclaimed from the exhaust air at the IEC and the SHE reduces the heating coil energy consumption significantly in the proposed system. It was also found that the IDECOAS consumes more fan energy than the conventional VAV, but this penalty is offset by the heating energy reduction.