Parameter estimation for ventilated photovoltaic façades

In this paper, the estimation of thermal parameters that describe the performance of ventilated photovoltaic (PV) façades integrated into buildings is investigated. In the most simpli” ed representation of the thermal characteristics of the building, the key factors are the coef” cients of solar heat gain and total heat loss. For an integrated building with a ventilated PV façade, a more accurate representation involves the interactions between the interior space, the ventilated space of the façade construction, the exterior PV elements, and the outside environmental conditions. The heat loss from the interior consists of both losses to ambient and to the ventilation air via the inner glazing or panelling. A direct numerical approach has been developed to identify the parameters that describe these heat transfer processes. The method allows the heat transfer coef” cients to be obtained directly from data measured on an operational ventilated PV façade. The results are compared with values taken from conventional practice.

Download Full-text

Heat-Loss Calculations in a SCWR Fuel-Channel

18th International Conference on Nuclear Engineering: Volume 2 ◽

10.1115/icone18-30069 ◽

2010 ◽

Author(s):

Wargha Peiman ◽

Eugene Saltanov ◽

Kamiel Gabriel ◽

Igor Pioro

Keyword(s):

Heat Transfer ◽

Heat Loss ◽

Nuclear Power ◽

Heat Losses ◽

Heat Transfer Analysis ◽

Operating Pressure ◽

Total Heat Loss ◽

Fuel Channel ◽

One Dimensional ◽

Heated Length

The objective of this paper is to calculate heat losses from a CANDU-6 fuel-channel while modifying it according to the specified operating pressure and temperature conditions of SuperCritical Water-cooled Reactors (SCWRs). Heat losses from the coolant to the moderator are significant in a SCWR because of high operating temperatures (i.e., 350–625°C). This has adverse effects on the overall thermal efficiency of the Nuclear Power Plant (NPP), so it is necessary to determine the amount of heat losses from fuel-channels proposed for SCWRs. Inconel-718 was chosen as a pressure tube (PT) material and PT minimum required thickness was calculated in accordance with the coolant’s maximum operating pressure and temperature. The heat losses from the fuel-channel were calculated along the heated length of the fuel-channel. Steady-state one-dimensional heat-transfer analysis was conducted, and programming in MATLAB was performed. The fuel-channel was divided into small segments and for each segment thermal resistances of the fuel-channel components were analyzed. Further, the thermophysical properties of the coolant, annulus gas, and moderator were retrieved from the NIST REFPROP software. The analysis outcome resulted in a total heat loss of 29.3 kW per fuel-channel when the pressure of the annulus gas was 0.3 MPa.

Download Full-text

A Comparative Numerical Study on Conjugate Natural Convection From Vertical Hollow Cylinder With Finite Thickness Placed on Ground and in Air

Journal of Thermal Science and Engineering Applications ◽

10.1115/1.4047568 ◽

2020 ◽

Vol 13 (2) ◽

Author(s):

Manoj Kumar Dash ◽

Sukanta Kumar Dash

Keyword(s):

Heat Transfer ◽

Nusselt Number ◽

Natural Convection ◽

Heat Loss ◽

Hollow Cylinder ◽

Average Nusselt Number ◽

Total Heat ◽

Outer Diameter ◽

Thermal Plume ◽

Total Heat Loss

Abstract The present work reports a comparative analysis of natural convection heat transfer from a thick hollow vertical cylinder either placed on the ground or suspended in the air. The numerical simulations have been performed by varying the cylinder length to its outer diameter (L/Do) in the range of 0.2–20, the thickness ratio (Di/Do) in a range of 0.5–0.9, and Rayleigh number (Ra) from 104 to 108. The flow and heat transfer characteristics have been delineated precisely with the presentation of the thermal plume and flow field in the vicinity of the cylinder. The variation of average Nusselt number (Nu), local Nu, and contribution to total heat loss from different surfaces with the pertinent parameters have been elucidated graphically. The average Nu is always more for the cylinder in the air compared with the case when it is on the ground. However, the difference between the Nu for these two cases diminishes, as the L/Do increases. It has also been found that the contribution to total heat loss from the inner surface of the hollow cylinder suspended in air increases with L/Do, attains a peak, and decreases sharply. Cooling time curves for the cylinder placed in air or on the ground have been described precisely. Finally, a correlation for the average Nusselt number as a function of all the pertinent parameters has been proposed that can be useful for industrial and academic purposes.

Download Full-text