Old Cooling Methods Benefit from Using New Technology

冷却塔控制系统取决于准确可靠的湿度测量，以提高能源效率并降低维护成本。

Cooling towers are among the oldest and most effective methods of removing heat from a building. Unfortunately, tradition can lead operators to use familiar but unreliable
导致损害塔效率的相对湿度（RH）测量不准确的设备。采用先进技术以准确可靠的RH和温度
measurements is essential for lowering energy use and maintenance costs.

Purpose is to Remove Heat

在HVAC应用中，在HVAC系统的冷却器中，蒸发冷却塔从冷凝器水中取出冷却水（用于冷却制冷剂的水）。在制冷剂到水的热交换过程中，制冷剂温度降低，冷凝器水温升高。然后将加热的冷凝器水循环到冷却塔中，将其喷洒或溅到复杂的通风表面上，最大化蒸发，从而从水中除去热量。然后将冷却的冷凝器水返回到冷却器中以继续周期。

Wet-bulb Temperature Sets Cooling Limit

冷凝水可以冷却多少受塔设计，塔数量，包括风扇和泵在内的操作设备以及环境因素的限制 - 可以是
冷却仅与室外湿块温度一样低，这是RH和温度的功能。在一个完美高效的冷却塔中，离开塔的水与湿块温度一样冷。由于没有塔没有非常有效的效率，因此塔设计师考虑了确定方法的局限性 - 方法是离开塔的水的可能温度和逼真的温度之间的实际差异。

将方法添加到湿块温度中，以确定实际的冷凝器水设定点。例如，使用4°C（7°F）接近的21°C（70°F）湿泡体温度
results in an actual setpoint of 25°C (77°F) for condenser water discharged from the tower. “Wet-bulb temperature measurement is similar to a temperature gauge in your car. It tells you how hard you can run the engine,” says Tim Wilcox of WPI, a U.S.-based consulting firm specializing in energy efficiency on a broad range of projects. “Its information is also used like the speed governor to avoid overrunning the equipment. Inaccurate measurement in either case can do great harm,” he adds.

Sources of Error

不准确的RH传感器是错误的湿泡温度，误导性控制系统和操作员的常见来源。错误的另一个来源也是找到RH传感器
close to the cooling tower, where it is affected by discharge air. Since the wet-bulb measurement must be true measurement of the outdoor ambient air, the RH device needs to be located away from any discharge air. “If the control systems are receiving a wet-bulb reading much cooler than possible, the operating engineers or the controls will attempt to
drive down the condenser water temperatures by engaging more pumps, fans and tower cells. The hardware can’t achieve the bogus temperature but the false information will
废物能量和风险污染 - 如果不损害 - 冷却塔。二流的RH设备将导致不可能的情况。” Wilcox说。

超额奔跑的成本

过度运行会导致可避免的运营和资本成本的几个领域：浪费能量以超出所需的粉丝，设备维修，加速度加速
of mineral build up in the tower fill, and inefficient water use from adding more water to the sump to replace the evaporated water. In one case that Wilcox cites, investigations concluded that inaccurate readings from an on-site RH device contributed to a cooling tower at a landmark hotel being so excessively run that the tower fill became nearly rock solid with calcium carbonate deposits. Uneven air flow rising through the plugged fill caused the tower system to be on the verge of shaking apart, damaging the fans and fan shrouds. Operators used fire hoses to keep the chiller plant operating at the height of the summer tourist season. Avoidable capital costs added up to hundreds of thousands of dollars to replace the tower fill.

Vaisala建议“湿度测量需要准确且可维护。我们指定VAISALA湿度传感器，我们可以依靠不迁移到错误。我们避免推荐可以在六个月内进行校准的仪器，从而误解了控制系统和建筑运营商。” Wilcox说。“我们看到可以花费的项目
$200,000 a year on cooling tower related operating costs operated by a $50 sensor that goes unreliable in months. Life is too short to deal with error-prone devices.”

The Vaisala Humicap® HMT330 Series Humidity and Temperature Transmitter delivers high accuracy and excellent long-term stability, even in harsh outdoor conditions. RH accuracy is within 1% up to 90% RH and within 1.7% up to 100% RH. Temperature accuracy is within 0.2°C (0.36°F). The transmitters calculate wet-bulb temperature and can be field calibrated to meet the operator’s quality management protocol.

准确性导致免费冷却

Wilcox recently reviewed cooling tower performance at an undisclosed data center in Utah. One of the recommended upgrades was to replace their RH device with the more accurate
Vaisalainstrument. Now using accurate RH in the wet-bulb temperature measurement, the facility could reduce energy costs by using more free cooling. Free cooling can be used when the outdoor wet-bulb temperature plus the approach is lower than the requirement for primary chilled water. Under these conditions, the condenser water cools the primary
冷水，完全绕过冷水机。自由冷却可降低机械冷却成本，更节能，并且被认为是绿色能源的努力。通过准确的湿泡温度测量值，数据中心能够在半年以上转换为免费冷却，并且仍然满足其冷却要求。

新方法更好

The value of accurate RH measurements is increasing as more cooling tower builders, operators, and HVAC professionals learn – still too often the hard way – that more reliable
使用先进技术的传感器可以多次为自己支付。