SGHF-1001 58113972 F 5761625-3D 用于DDC接线板 ABB

SGHF-1001 58113972 F 5761625-3D 用于DDC接线板 ABB

SGHF-1001 58113972 F 5761625-3D 用于DDC接线板 ABB

真空系统和设备。能量的增加

在20世纪70年代，设备成本导致广泛接受

新方法，因为一般来说，如果设备尺寸过大，总体运行效率会降低。即使如此，表中的因素

保守，通常会导致一些尺寸过大。

3.8通风负荷

渗透已经讨论过了。然而，大多数建筑规范

公共建筑需要强制通风，采用固定通风

与占用率相关的费率。而较旧的代码使用5到

每人10立方英尺/分钟，当前要求使用两到三次

这个数量。大多数地方建筑规范使用全部或部分ASHRAE

以标准62为基础。本标准不断修改，当前版本日期为2001年。某些规范可能允许：

根据室内空气质量测量自动调整外部空气量。测量值可包括CO2和/或

挥发性有机碳（VOC）。

此外，许多工艺需要大量排气，以

需要该补充空气。用于通风和补给的外部空气

必须通过空气处理装置引入，在空气处理装置中进行过滤和回火（达到加热或冷却的设计条件设计程序：***部分

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78第三章

ing）。由于知道以下情况，整个问题变得更加复杂：

在许多室内环境中，室外空气质量可能不可接受，因此可能需要进行特殊处理以去除污染物（见第5章和第21章）。

因此，虽然通风负荷不是空间负荷的一部分，但它是

反映在空气处理装置和中央设备容量中。对于加热，它是最小外部空气量乘以设计

温差和适当的空气系数。因此

q
CFM 1.08（t t）（3.7）h oa输入输出

式中：qh
供暖通风负荷，Btu/h

设计内部温度、加热

设计外部温度、加热

CFMoa
外部空气量，ft3/min

1.08
空气系数，Btu/h/[（ft3/min）

F]（对于标准空气必须

针对较高标高进行调整）

对于冷却，通风负荷为最小外部空气量

乘以设计焓差。因此

q
CFM（h h）0.075 60（3.8）t oa o i

式中：qt
通风总冷负荷，Btu/h

设计外部条件下的焓，Btu/lb

设计内部条件下的高焓，Btu/lb

0.075
空气密度，lb/ft3（对于标准空气，必须调整

高海拔）

60分钟/小时

显冷负荷根据设计温度计算

差别因此

q
CFM（t t）1.08（3.9）s oa o i

式中：qs
通风显冷，Btu/h

至外部设计温度，冷却

内部设计温度，冷却

如第4章所示，如果根据湿度图分析计算空气处理机组容量，则通风负荷将自动包括在内。

请注意，没有热损失的内部区域可以利用外部

如果空气处理系统如此设计，则为冬季冷却提供空气。这

将导致通风热负荷的一些降低。

设计程序：***部分

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任何使用均受网站上给出的使用条款的约束。

设计程序：***部分79

3.9其他荷载

还有一些其他因素有助于冷却和

热负荷。其中包括风扇和泵工作以及管道

以及管道损失。这些将在后续章节中讨论。

无论如何，热力学***定律占上风。能量是

既没有创造也没有毁灭。如果能量进出建筑物，必须对其进行核算

SGHF-1001 58113972 F 5761625-3D 用于DDC接线板 ABB

SGHF-1001 58113972 F 5761625-3D 用于DDC接线板 ABB

VAC systems and equipment. The increases in energy

and equipment costs during the 1970s led to a broad acceptance of the

new methods because, in general, overall operating efficiency decreases if equipment is oversized. Even so, the factors in the tables

are conservative, and some oversizing will normally result.

3.8 Ventilation Loads

Infiltration has already been discussed. However, most building codes

require positive ventilation in public buildings, with a fixed ventilation

rate which relates to occupancy. While older codes used rates of 5 to

10 ft3 /min per person, current requirements use two or three times

that amount. Most local building codes use all or part of ASHRAE

Standard 62 as a basis. This Standard undergoes continuous modification—the current issue is dated 2001. Some codes may allow for

automatic adjustment of outside air quantities, based on measurement of indoor air quality. Measured values may include CO2 and/ or

volatile organic carbons (VOC) as appropriate.

In addition, many processes require large amounts of exhaust, for

which makeup air is required. Outside air for ventilation and makeup

must be introduced through an air-handling unit, where it can be filtered and tempered (brought to design condition for heating or coolDesign Procedures: Part 1

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78 Chapter Three

ing). This whole matter is further complicated by the knowledge that

outdoor air quality may not be acceptable in many indoor environments, so that special treatment to remove contaminants may be necessary (see Chaps. 5 and 21).

Thus, while the ventilation load is not a part of the space load, it is

reflected in the air-handling unit and central plant capacity. For heating, it is the minimum outside air quantity multiplied by the design

temperature difference and the proper air factor. Thus,

q
CFM  1.08  (t  t ) (3.7) h oa i o

where qh
ventilation load for heating, Btu/h

ti
design inside temperature, heating

to
design outside temperature, heating

CFMoa
outside-air quantity, ft3 /min

1.08
air factor, Btu/h/[(ft3 /min)

F] (for standard air—must

be adjusted for higher elevations)

For cooling, the ventilation load is the minimum outside air quantity

multiplied by the design enthalpy difference. Thus,

q
CFM  (h  h )  0.075  60 (3.8) t oa o i

where qt
total cooling load for ventilation, Btu/h

ho
enthalpy at design outside conditions, Btu/ lb

hi
enthalpy at design inside conditions, Btu/ lb

0.075
air density, lb/ ft3 (for standard air—must be adjusted for

higher elevations)

60
min/h

The sensible cooling load is calculated from the design temperature

difference. Thus,

q
CFM  (t  t )  1.08 (3.9) s oa o i

where qs
sensible cooling for ventilation, Btu/h

to
outside design temperature, cooling

ti
inside design temperature, cooling

If the AHU capacity is calculated from a psychrometric chart analysis, as shown in Chap. 4, the ventilation load is automatically included.

Notice that interior zones, with no heat loss, can make use of outside

air for winter cooling if the air-handling system is so designed. This

will result in some reduction of the ventilating heating load.

Design Procedures: Part 1

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Design Procedures: Part 1 79

3.9 Other Loads

There are some additional factors which contribute to the cooling and

heating loads. Among these are fan and pump work as well as duct

and piping losses. These are discussed in subsequent chapters.

In any case, the first law of thermodynamics prevails. Energy is

neither created or destroyed. If energy moves into or out of the building, it must be accounted