| Cleanroom is required to meet the following three conditions in order to reach the requiredcleanliness class: first, air filter should be high efficiency;secondly, there should be sufficient airsupply;thirdly, the flow pattern of the air-flow should be reasonable. While adoptingreasonable airflow distribution scheme in room can decrease greatly air supply .New type of inlets and airflow pattern are adopted. Meeting the cleanliness class requiredby the cleanroom with as less uncontaminated air as possible is recognized to be an importantmeasure for energy saving and cost reducing. Vector-flow cleanroom, as a new and energy-savingcleanroom, has been widely used in other countries, yet, its application leaves nearly blank inChina.This paper seeks for the feasibility of applying vector flow to air-conditioning of cleansickroom in hospital.By combining CFD simulation and model experiment, the paper studies the airflowdistribution in vector-flow clean sickroom. The CFD simulation is carried out by simulating oncomputer the indoor airflow field of the vector-flow clean sickroom under non-built and as-builtstation on the basis of κ-εdouble-equation turbulent flow model, by means of limited volumemethod and using airpak commercial software package, thus educing the distribution characteristicof indoor flow field. Through model experiment, the indoor flow field of the vector-flow cleansickroom under as-built condition is tested, and test result of the indoor flow field is given.Moreover, point contaminating source is set in the room to simulate the emitting situation of thecontaminator from patients in the sickroom, and indoor concentration field is measured, then thedischarging characteristic of contaminator in the clean sickroom is accordingly educed. In addition,with same air supply volume and filter area as well as same return air mode, indoor concentrationfields formed by turbulent-flow schemes are tested, further, comparison is made between such twoairflow distribution schemes.Results indicate that the results from numerical calculation accord well with those out ofexperiment both quantitatively and qualitatively. By fixing sector diffusion orifice plate outsidethe high efficiency particular air filter, the indoor airflow field is better than that under air blastingdirectly by the high performance filter. The hole percentage of the sector diffusion orifice plateshould between 0.15 and 0.3, with the best of 0.2. The high efficiency particular air filter can bearranged on the roof or side wall according to the site condition. But if the filter is on the roof, itwill give a better effect in indoor flow field compared with on side wall. With the length of theroom increases, the flow field within the working area in the middle of the room transits fromvertical laminar flow to approximately horizontal laminar flow, but it is not as good as thehorizontal laminar flow in terms of speed uniformity. When the clean sickroom is arranged withsickbeds, the indoor airflow will be disturbed and blocked to some extent. Whereas, apart from thearea around sickbeds, the flow field within other part of the room is basically identical with thatunder non-built condition . It should be better to place sickbeds at the middle and back parts of theroom. The more the sickbeds are near the return air out-let , the more the harmful substance iseasily discharged. Due to the restraining function of approximately unidirectional airflow, it ishard for dust particles in the vector-flow cleanroom to diffuse reversely, accordingly, the area infront of the point contaminating source is held uncontaminated basically. Under such airflowdistribution, contaminator will diffuse transversely in a small amount and can be rapidlydischarged from the return air out-let. Thus, it is a relatively ideal flow pattern of air-flow. |
