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对于VAV，最小设计速率应约为0.75至1.0

（ft3/min）/ft2

，这将导致建筑物平均实际循环

速率为0.5至0.6（ft3/min）/ft2

.高于3.0（ft3/min）/ft2的值可以创建

分布问题，高速气流作用在乘客身上。如果

重新检查计算表明，这些高气流是必要的，因此应特别注意空气分配技术。洁净室和大型计算机室通常需要气流

8至10（ft3/min）/ft2的速率

.处理方法见第5章

这些是利率。

经验表明，小幅调整后的高利率下降

高达3.0和低至0.75（ft3/min）/ft2的速率将导致较少的问题

而不是使用计算的速率。同样，判断和常识

需要。

上述评论意味着系统概念必须先于

计算。也就是说，在进行总结之前，必须至少对要使用的HVAC系统类型、分区、设备位置和控制策略进行近似。虽然这不是一个abDesign程序：***部分

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设计程序：***部分77

溶质要求，这将使计算过程更加高效。

概念应灵活，以适应所需的变化

由于不可预见的并发症和***一分钟的使用变更

以及占用某些建筑空间。

此注释扩展到管网的尺寸。多年后

从经验来看，似乎谨慎的做法是偏大一点，

而不是有点太小。

3.7动态与静态

负荷计算

所有手动负荷计算和许多计算机程序都假设存在静态或稳态条件。但是稳态

空调情况下不存在条件。如果暖通空调

如果系统和控制功能正常，则室内环境将略有变化。然而，内部和外部

负载不断变化。冷负荷系数的函数

计算中的（CLF）是近似这些瞬态的影响

使静荷载计算产生更类似结果的因素

“真实”动态负载。

导致这些因素的研究源于广泛的

公认的条件是，旧的计算方法总是导致

暖通空调系统和设备尺寸过大。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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For VAV a minimum design rate should be about 0.75 to 1.0

(ft3 /min)/ ft2

, which will result in a building average actual circulation

rate of 0.5 to 0.6 (ft3 /min)/ ft2

. Values above 3.0 (ft3 /min)/ ft2 can create

distribution problems, with high-velocity drafts on the occupants. If a

recheck of the calculations shows that these high airflows are necessary, then special attention should be paid to the air distribution technique. Clean rooms and large computer rooms typically need airflow

rates of 8 to 10 (ft3 /min)/ ft2

. See Chap. 5 for methods of dealing with

these rates.

Experience has shown that small adjustments of high rates down

to 3.0 and low rates up to 0.75 (ft3 /min)/ ft2 will cause fewer problems

than using the calculated rates. Again, judgment and common sense

are needed.

The above comments imply that the system concept must precede

the calculations. That is, the types of HVAC systems to be used, zoning, location of equipment, and control strategies must be at least approximated before the summaries are made. While this is not an abDesign Procedures: Part 1

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Design Procedures: Part 1 77

solute requirement, it will make the calculation process more efficient.

The concept should be flexible, so as to accommodate changes required

by unforeseen complications and last-minute alterations in the use

and occupancy of certain building spaces.

This comment extends to the sizing of ductwork. After many years

of experience, it seems prudent to err on the side of a little too large,

rather than a little too small.

3.7 Dynamic versus Static

Load Calculations

All manual load calculations and many of the computer programs assume that a static or steady-state condition exists. But steady-state

conditions do not exist in an air conditioning situation. If the HVAC

systems and controls are functioning properly, then the indoor environment will vary only slightly. However, the internal and external

loads are constantly changing. The function of the cooling load factor

(CLF) in the calculation is to approximate the effect of these transient

factors so that the static load calculation will yield results more like

the ‘‘real’’ dynamic load.

The research which led to these factors resulted from the widely

recognized condition that older calculation methods invariably led to

oversizing of HVAC 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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