# Enhancing Air Quality for Embedded Hospital Germicidal Lamps

## Abstract

**:**

## 1. Introduction

^{3}/h. Zhou et al. [14] demonstrated numerically that improper air ventilation could lead to cross-infection due to air transmission in hospitals. Following these approaches, in this study, germicidal filters were combined with fans and installed in hospital lighting to improve the air quality of hospitals. The effectiveness of three designs was examined using flow simulations to obtain the largest air flow rate under the condition of a fixed fan speed before the actual implementation of the design. Then, the design that showed good performance was implemented and tested. Thus, both air quality and fan energy-saving can be achieved simultaneously and more economically. Details of the simulation approach, results and discussion, and conclusions are presented as follows.

## 2. Simulation Approach

#### 2.1. Governing Equations

- (a)
- x-direction momentum equation$$\begin{array}{l}\rho \frac{\partial U}{\partial t}+\rho U\frac{\partial U}{\partial x}+\rho V\frac{\partial U}{\partial y}+\rho W\frac{\partial U}{\partial z}\\ =\frac{\partial P}{\partial x}+\frac{\partial}{\partial x}\left[2\left(\mu +{\mu}_{t}\right)\frac{\partial U}{\partial x}\right]+\frac{\partial}{\partial y}\left[\left(\mu +{\mu}_{t}\right)\left(\frac{\partial U}{\partial y}+\frac{\partial V}{\partial x}\right)\right]+\frac{\partial}{\partial z}\left[\left(\mu +{\mu}_{t}\right)\left(\frac{\partial U}{\partial z}+\frac{\partial W}{\partial x}\right)\right]\end{array}$$
- (b)
- y-direction momentum equation$$\begin{array}{c}\rho \frac{\partial V}{\partial t}+\rho U\frac{\partial V}{\partial x}+\rho V\frac{\partial V}{\partial y}+\rho W\frac{\partial V}{\partial z}\\ =\frac{\partial P}{\partial y}+\frac{\partial}{\partial x}\left[\left(\mu +{\mu}_{t}\right)\left(\frac{\partial U}{\partial y}+\frac{\partial V}{\partial x}\right)\right]+\frac{\partial}{\partial y}\left[2\left(\mu +{\mu}_{t}\right)\frac{\partial V}{\partial y}\right]+\frac{\partial}{\partial z}\left[\left(\mu +{\mu}_{t}\right)\left(\frac{\partial V}{\partial z}+\frac{\partial W}{\partial y}\right)\right]\end{array}$$
- (c)
- z-direction momentum equation$$\begin{array}{c}\rho \frac{\partial W}{\partial t}+\rho U\frac{\partial W}{\partial x}+\rho V\frac{\partial W}{\partial y}+\rho W\frac{\partial W}{\partial z}\\ =\frac{\partial P}{\partial z}+\frac{\partial}{\partial x}\left[\left(\mu +{\mu}_{t}\right)\left(\frac{\partial U}{\partial z}+\frac{\partial W}{\partial x}\right)\right]+\frac{\partial}{\partial y}\left[\left(\mu +{\mu}_{t}\right)\left(\frac{\partial V}{\partial z}+\frac{\partial W}{\partial y}\right)\right]+\frac{\partial}{\partial z}\left[2\left(\mu +{\mu}_{t}\right)\frac{\partial W}{\partial z}\right]\end{array}$$$${\mu}_{t}={C}_{\mu}\rho \frac{{k}^{2}}{\epsilon}$$

#### 2.2. Lamp and Fan Geometries

#### 2.3. Material Properties

#### 2.4. Simulation Steps

- (1)
- Model Definition and Simplification

- (2)
- Boundary Conditions

- (3)
- Fan Performance Curve

- (4)
- Filter Resistance Curve

- (5)
- Mesh and convergence test

## 3. Results and Discussion

#### 3.1. Velocity Distribution in the Flow Channel (Z-Plane)

#### 3.2. Inlet/Outlet Velocity Distributions

^{3}/h (CMH), 66 CMH, and 12.8 CMH for Types 1, 2, and 3, respectively. Lastly, the volumetric outlet flow rates of Type 3 were increased by nearly 149.4%, taking those of Type 1 as a reference. For indoor ventilation, the uniformity of the flow field at the outlets is essential. Hence, the design of Type 3 performs better in both flow uniformity and flow rate.

#### 3.3. Lamp Module Operation Point

## 4. Conclusions

## Funding

## Institutional Review Board Statement

## Informed Consent Statement

## Data Availability Statement

## Conflicts of Interest

## References

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**Figure 4.**Fan Performance Curve [16].

**Figure 5.**Filter Resistance Curve [17].

Item | Unit | Air | Plastic |
---|---|---|---|

Density | kg/m^{3} | 1.2047 | 432.54 |

Viscosity | Pa-s | 1.817 × 10^{−5} | — |

Conductivity | W/m-K | 0.02563 | 0.259843 |

Specific Heat | J/kg-K | 1004 | 837 |

k-ε Model | Constant | Value | |

${C}_{\mu}$ | 0.09 | ||

${C}_{1}$ | 1.44 | ||

${C}_{2}$ | 1.92 | ||

${\sigma}_{K}$ | 1.0 | ||

Boundary conditions | Types 1, 2, and 3 | inlet | Pressure 0 Pa (Gage) |

outlet | |||

Mesh conditions (number of nodes and elements) | Type 1 | Fluid | Nodes: 558,526; Elements: 1,618,093 |

Solid | Nodes: 39,475; Elements: 484,726 | ||

Type 2 | Fluid | Nodes: 355,004; Elements: 1,060,911 | |

Solid | Nodes: 28,135; Elements: 304,958 | ||

Type 3 | Fluid | Nodes: 472,322; Elements: 1,520,467 | |

Solid | Nodes: 31,239; Elements: 353,267 |

Item | Type 1 | Type 2 | Type 3 | |
---|---|---|---|---|

Inlet | Inlet 1 | 64 | 87.3 | 94.8 |

Inlet 2 | 63.7 | 87.3 | 93.5 | |

Inlet 3 | 62.1 | 86.9 | 95.5 | |

Inlet 4 | 62.1 | 86.8 | 92.5 | |

Sum | 251.9 | 348.3 | 376.3 | |

Increase rate | 100% | 138.3% | 149.4% | |

Outlet | Outlet 1 | 135 | 50 | 98.7 |

Outlet 2 | −10.4 | 116 | 86.4 | |

Outlet 3 | 135.5 | 68.5 | 97.5 | |

Outlet 4 | −10.8 | 110.1 | 85.9 | |

Sum | 249.3 | 344.6 | 368.5 | |

Increase rate | 100% | 138.2% | 147.8% |

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**MDPI and ACS Style**

Chen, J.-S. Enhancing Air Quality for Embedded Hospital Germicidal Lamps. *Sustainability* **2021**, *13*, 2389.
https://doi.org/10.3390/su13042389

**AMA Style**

Chen J-S. Enhancing Air Quality for Embedded Hospital Germicidal Lamps. *Sustainability*. 2021; 13(4):2389.
https://doi.org/10.3390/su13042389

**Chicago/Turabian Style**

Chen, Jung-Shun. 2021. "Enhancing Air Quality for Embedded Hospital Germicidal Lamps" *Sustainability* 13, no. 4: 2389.
https://doi.org/10.3390/su13042389