Numerical and Experimental ......(18)

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Numerical and Experimental Investigation of Building-Integrated Photovoltaic-Thermal Systems绿色建筑博客 ]%t:\9zd

LITERATURE REVIEW

Limitations & Disadvantages:

(1) Most of the data obtained using hot-wire anemometry is limited to small perturbations. There are cases where this linearization of the anemometry equation is not accurate and nonlinear effects can influence both the mean and fluctuating voltages (Corrsin 1943; Hinze 1975).

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(2) Because of the mass associated with the wire supports, there can be a significant amount of heat loss from the wire due to conduction to the relatively cold supports. This heat loss results in a spanwise temperature distribution along the wire, which, in turn, causes a variation of heat transfer from the wire along its length (Kovasznay 1959; Sandborn 1972; Lowell 1950).绿色建筑博客2oeKz*~SL

(3) Near wall or surface measurement can introduce errors due to increased heat transfer from the wire due to conduction to the relatively cold walls. There are cases that a hot-wire calibrated under free-stream conditions measures the velocity too high in the viscous sublayer due to this near-wall effect. (Durst 2001; Dantec Dynamics website www.dantecdynamics.com)

(4) At very low velocities the heated wire can cause a relatively significant vertical movement of the fluid due to buoyancy effects on the lower density fluid adjacent to the wire. So there is always a lowest velocity limit for Hot-Wire Anemometry (Andrews and Bradley 1972).

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(5) Hot-Wire Anemometry can only provide velocity measurement at a single point in space over time. Since the Anemometry has to touch the fluids, it may disturb the flow domain in some measure (Mohammad 2002).