Conventional Receiver Design Research Articles

Numerical and experimental analysis of a cross-finned solar receiver for parabolic dish collectors

A parabolic dish solar collector (PDC) is used to concentrate solar radiation on a receiver to produce hot water or steam for various thermal applications. The solar receiver of the PDC is one of the significant components to improve the overall efficiency of the PDC. The present study is a numerical and experimental investigation of the thermal performance of a solar receiver with vertical fins with and without cross fins. The fin orientation was investigated using 0.056 kg/s, 0.083 kg/s, and 0.111 kg/s water flow rates. COMSOL Multiphysics® was used to simulate the receiver to determine the receiver’s temperature behavior. The thermal performance parameters such as heat gain, heat loss, convective heat transfer coefficient, and thermal, and exergy efficiency were analyzed under various flow conditions. The cross fins effectively prolong the water residence, increasing turbulence, and heat transfer and reducing heat loss to the surroundings. The receiver with cross fins at higher flow rate conditions shows higher thermal performance than lower flow rate and without fins conditions. The solar radiation during the outdoor testing is in a range of 300–950 W/m2 and the ambient temperature varies from 30-37 °C. The peak average thermal and exergy efficiency obtained for the cross-finned receiver at 0.111 kg/s is 64.4 %, and 6.3 %, respectively. Cross-finned receiver operating at 0.111 kg/s reduced CO2 mitigation rate, estimated at approximately 0.29 tons of CO2 per year, along with a lower carbon credit gain at $0.47. Thus, the proposed cross-fin solar receiver demonstrates improved thermoeconomic performance than conventional receiver designs, offering a more cost-effective design with minimal investment.

Applicability of Heat Mirrors in Reducing Thermal Losses in Concentrating Solar Collectors

Abstract In the present work, a novel parabolic trough receiver design has been proposed. The proposed design is similar to the conventional receiver design except for the envelope and the annulus part. Here, a certain portion of the conventional glass envelope is coated with Sn-In2O3 and also Sn-In2O3 coated glass baffles are provided in the annulus part to reduce the radiative losses. The optical properties of the coated glass are such that it allows most of the solar irradiance to pass through, but reflects the emitted long wavelength radiations back to the absorber tube. Sn-In2O3 coated glass is referred to as “transparent heat mirror.” Thus, effectively reducing the heat loss area and improving the thermal efficiency of the solar collector. A detailed one-dimensional steady-state heat transfer model has been developed to predict the performance of the proposed receiver design. It was observed that while maintaining the same external conditions (such as ambient/initial temperatures, wind speed, solar insolation, flow rate, and concentration ratio), the heat mirror-based parabolic trough receiver design has about 3–5% higher thermal efficiency as compared to the conventional receiver design. Furthermore, the heat transfer analysis reveals that depending on the spatial incident solar flux distribution, there is an optimum circumferential angle (θ = θoptimum, where θ is the heat mirror circumferential angle) up to which the glass envelope should be coated with Sn-In2O3. For angles higher than the optimum angle, the collector efficiency tends to decrease owing to increase in optical losses.

Interference-aware self-optimizing Wi-Fi for high efficiency internet of things in dense networks

Wi-Fi is one of the candidate technologies for the Internet of Things (IoT), and today connects billions of devices world-wide in dense networks to offer Internet connectivity in a partially or fully automated manner. In order to provide seamless and high quality service, wireless local area networks (WLANs) can adopt dynamic channel access technologies such as dynamic bandwidth or channel hopping schemes in order to avoid interference for better link quality. However, in dense networks, the dynamic channel access leads to a higher probability of adjacent channel interference (ACI). The efficiency of IEEE 802.11-based WLANs using multi-channel and wide dynamic ranges is thus severely degraded by ACIs in dense networks. In this paper, we analyze the ACI effect on WLANs and propose an interference-aware self-optimizing (IASO) Wi-Fi design that incorporates a multi-channel multi-level carrier sense and adaptive initial gain control scheme. This scheme controls carrier sensing thresholds in each band for multi-level sensors, as well as initial gains for amplifiers. The proposed scheme reduces false carrier sensing and avoids saturation of amplifiers while simultaneously improving the dynamic range of the receiver. Our prototype evaluation results demonstrate that the proposed scheme can improve the dynamic range of the receiver by approximately 45dB and 30dB for a low data rate and a high data rate mode, respectively, compared with the conventional receiver designs. Furthermore, network emulation results demonstrate that the IASO Wi-Fi can improve the average throughput, latency, and energy efficiency by approximately 32% (24%), 41% (43%), and 13% (17%), respectively, compared with the conventional receiver designs (and channel hopping techniques) in dynamically varying interfered channel conditions.

Blind carrier frequency offset mitigation in space–time block‐coded multicarrier code division multiple access uplink transmission

SummaryIn this paper, a novel blind carrier frequency offset (CFO) estimation is proposed on the basis of the linearly constrained optimization for the uplink transmission of space–time block‐coded multicarrier code division multiple access systems. First, the full‐dimensional spatial‐and‐temporal data are formed to avoid violation of the second‐order statistics in the conventional receiver design. A set of weight vectors is then provided for acquiring each multipath signal from the desired user while the others get rejected. Finally, the estimated CFO is obtained in accordance with maximizing the well‐defined measurement function, which is formulated by collecting all the output powers of the receiver. A space–time averaging technique is also proposed to enhance the robustness to the finite sample effect. Simulation study confirms that with the proposed CFO estimator used in the preceding, the receiver can successfully achieve the same performance of the optimal receiver working in the absence of CFO. Copyright © 2014 John Wiley & Sons, Ltd.

A Decision Feedback Reverse Link Receiver Implementation for IS-95 CDMA Communications

An implementation of a reverse link receiver for IS-95 CDMA (Code-Division Multiple-Access) communications that applies decision feedback to the decoding of the received signal is presented. Decision feedback is used in order to improve BER performance by making use of additional information that conventional receiver designs generally ignore. Qualitative analysis and computer simulation of the hardware components of the proposed implementation shows that it can be built as a single integrated circuit using present day technology. The design presented here does not include the RF front-end of the receiver, does not consider the effects of multipath and fading on system performance, and assumes perfect power control.