热进……热出：与 HVAC 专家 Joe Joe 聊聊热传递 - 第281期短片

嗨。

Hey.

嗨。

Hey.

我是布莱恩。

This is Brian.

这是一集由乔伊·亨德森——也就是大家熟知的空调师傅Jojo，YouTube上的HVAC专家Jojo——带来的短节目，主题是热量的输入与输出。

This is a short episode about heat in, heat out by Joey Henderson, also known as Jojo, the HVAC man, J o e j o e, the HVAC man on YouTube.

去关注一下他吧。

Check him out.

订阅他的频道。

Subscribe to his channel.

乔伊是一位资深讲师，平时经常讲通风气流，但这一集我们主要聊的是基础热力学。

Joey's a longtime instructor, does a lot of talking about airflow in general, but in this episode, we're talking about basic thermodynamics.

热量进来，热量出去。

Heat in and heat out.

在开始之前，我们要感谢我们的优秀赞助商。

Before we do that, we wanna thank our great sponsors.

开利公司和 carrier.com。

Carrier and carrier.com.

开利一直是这个播客的长期赞助商。

Carrier has been a long term sponsor of the podcast.

他们从很早就支持我们做这些事，而且我们每天销售的产品就是他们的。

They've made it possible very early on for us to do what we do, and they are the products that we sell day in and day out.

从单级设备到绿色极速系列，那是目前市场上最高效的设备之一。

Everything from single stage equipment all the way up to the green speed extreme, one of the most efficient products on the market today.

想了解更多开利的产品，或者如何成为开利经销商，请访问 carrier.com。

Find out more about what Carrier has to offer and about becoming a Carrier dealer by going to carrier.com.

制冷科技公司，网址是 refrigeratech.com，特别是他们新推出的 Viper 湿布热屏蔽垫。

Refrigeration technologies at refrigeratech.com and specifically the new Viper Wet Rag Heat Shield.

这是一种革命性的阻燃焊接垫，可以干用，也可以湿用。

The revolutionary flame resistant welding pad designed to be used either wet or dry.

在您附近的经销商那里购买Viper湿布隔热垫，或者访问truetechtools.com，结账时使用优惠码GETSCOOLED，享受超值折扣。

Find a Viper wet rag heat shield at a distributor near you or go to truetechtools.com and use offer code GETSCOOLED for a great discount at checkout.

Copeland和White Rogers的47D01U-843型号。

Copeland and the White Rogers forty seven d zero one u dash eight four three.

别忘了这一点。

Don't forget that.

别忘了这一点。

Don't forget that.

把它记下来。

Write it down.

这是通用热泵除霜控制器。

Universal heat pump defrost control.

没错，就是这个。

That's what it is.

这是一款真正的通用部件，兼容超过400种零件编号。

It's a truly universal part compatible with over 400 part numbers.

几乎所有的单级除霜控制器都适用。

Virtually every single stage defrost control.

车上常备这一款零件非常划算。

It's a great part to keep stocked on the truck.

我跟你说真的。

Trust me.

我知道，因为我们自己就在用。

I know because we do.

它内置了两种除霜模式：定时和按需。

It has two different defrost methods, timed and demand, built in.

我们推荐用按需模式。

We suggest demand.

切换起来很简单。

It's easy to convert over.

配件里已经包含了传感器。

It comes with the sensors.

除了减少不必要的循环外，按需除霜还内置了多项功能，能有效保护压缩机。

In addition to eliminating extra cycles, with demand defrost, it comes with multiple features that help protect the compressor.

它每六小时自动执行一次除霜循环，强制回油来保护压缩机，同时还具备欠压保护、短周期保护，以及断电恢复后随机延时启动的功能。

It runs a defrost cycle every six hours to force oil return and protect the compressor that way, and it comes with built in brownout protection, short cycle protection, and a random start delay when power comes back on after an outage.

根据原厂规格或自定义参数，设置起来又快又简单。

Quick and easy setup based on OEM specs or custom parameters.

更多详情请访问 hvacrschool.com/wr-defrost。

Find out more at hvacrschool.com/wr-defrost.

网址是 hvacrschool.com/wr-defrost。

That's hvacrschool.com/wr-defrost.

Field Peace 和 Field Peace University。

Field Peace and Field Peace University.

可以获取 NATE 学分，学习从抽真空、检漏到制冷剂等各类实用课程。

Get NATE credits, take amazing courses on everything from evacuation, leak detection, gas.

想了解更多信息？

Find out more.

前往 fieldpeace.com/fieldpeace-university。

Go to fieldpeace.com/fieldpeace-university.

就是 fieldpeace.com/fieldpeace-university。

That's fieldpeace.com/fieldpeace-university.

嗨。

Hey.

我是乔乔，做暖通空调的。

This is Jojo, the HVAC man.

我现在在 HVAC 学校第七届研讨会现场，今天佛罗里达的天气特别好。

I am here at the HVAC, our school's seventh annual symposium and it's a great beautiful day here in Florida.

天气真不错，咱们这个小校园里聚集了业内最顶尖的专家，氛围太棒了。

It's beautiful, we got some of the best minds in the industry right here on this little campus and it's been amazing.

所以有人请我来跟大家聊聊一个特别重要的主题——热传递。

And so I've been asked to talk with you guys about a subject matter I think that is super important and that is gonna talk about heat transfer.

我知道听起来挺枯燥的，像是工程课的内容，但咱们平时不就是干这个吗？

I know that sounds like a really boring topic, more like engineering, but that's what we do all the time, right?

所以我们先把设备启动起来。

So we get the unit running.

电气方面我们就搞定这个了。

So we got that on the electrical side.

如果你了解我，我的一贯原则就是越简单越好，因为我本人就是个简单的人。

If you know me, my whole motto is keep it simple because I'm just a simple guy.

明白吗？

Alright?

我搞不了那么复杂的东西。

I can't make it complicated.

我想把热传递的一些关键点简化成现场能直接用的方法，不用花上上万美元买专业设备，也不用当半个工程师就能判断设备是不是正常运行。

I wanna boil down some heat transfer facts down to what can we do in the field to make sure it's working right without having to pull out $10,000 worth of bat gear and become pseudo engineers to figure this thing out.

清楚吧？

Okay?

首先，我们来看看行业里对制冷量的标准是什么。

And so first of all, let's look at what the industry standards are for capacity.

当说这是一个两吨的机组，或者四吨、一百吨的机组时。

When it says it's a two ton unit or when it says it's a four ton unit or a 100 ton unit.

不过咱们先回头看看两吨的机组，好吧？

But let's go back to the two ton unit, all right?

对于风冷系统，厂家做容量图表时的标准是什么？

So an air cooled system, what are the standards when they do the capacity charts?

首先，你得知道他们是以什么条件来标定的。

Well, first of all, you got to know what they do the capacity in.

说到每小时英热单位，一吨就是一万二千英热单位，这个没问题。

And when we go into BTUs per hour, that's 12,000 BTUs per ton, no problem.

但一个三吨的机组，真的正好是三万六千英热单位吗？

But when a unit is a three ton unit, is it really exactly 36,000 BTUs?

答案是：不是的。

Well, the answer is no, it's not.

只有在特定条件下才是这样。

It's only at certain conditions.

这就像汽车的时速或油耗标称值，都是在特定轮胎、标准尺寸、固定胎压和理想路况下测出来的，可我们实际根本遇不上这种条件。

It's kinda like when they do miles per hour on a car or miles per gallon on a car, it's always at a certain set of tires and certain standard size and certain air pressure and certain road conditions, which we never get.

你永远达不到车贴上写的油耗数字，因为路况随时都在变。

You never get the miles per gallon that's on the sticker of the car because road conditions vary all the time.

轮胎状况也一直在变。

Tire conditions vary all the time.

我们在现场遇到的情况，其实就是这么回事。

Well that's kind of what we're up against in the field.

工厂设计机组时，所有厂商都得遵循一个标准：室外95华氏度，室内干球温度80华氏度、湿球67华氏度——也就是说，设备的制冷量是在室外95度、室内保持80度且相对湿度50%的条件下测出来的。

So in the factory, when they design a unit, the standard that all manufacturers have to go by is it's 95 degrees outside with, get this, capacity charger rated at 80 degrees dry bulb inside at 67 wet bulb, which equates to basically they are rating the capacities of this equipment when it's 95 degrees outside, maintaining 80 degrees inside at 50% relative humidity.

所有机组的额定容量，都是按这个标准来的。

That is where they rate all their units.

但你可能会想，等等，我们平时不都是设在75度吗？Manual J的计算标准也是75度室内温度，SEER效率评级也是基于75度。

Now you're like, well wait a minute, we're all setting them at 75 and that's where manual j conditions are, 75 degrees indoor at about 50% relative humidity and the SEER ratings were rated at 75 degrees indoor.

但额定制冷量却是按80度算的。

But the capacities are at 80.

你别怪我啊，我就是个传话的。

Now don't shoot me, I'm just the messenger when it comes to this.

当我们做负荷计算时，如果把室内设计温度从80度调到75度，就得重新调整设备来匹配这个温度。

Now when we adjust for a load calculation and we change the indoor design from 80 to 75, well then we have to readjust the equipment to fit that.

我刚开始学制冷量计算的时候，最让我惊讶的就是，标准是80度干球温度、67度湿球温度。

That's the first thing that was an eye opener to me when I was studying capacity charge, that it was 80 degree dry bulb, 67 wet bulb.

这也让我想到下一个问题：干球温度到底是什么？湿球温度又是什么？

And that also leads to me the next question is, well, what the heck is a dry bulb and what the heck is a wet bulb?

干球温度就是我们一直用的温度探头测出来的那种温度。

Well, a dry bulb is what we've been measuring forever and ever with a temperature probe out of our pocket.

我们掏出探头，往回风管或送风管里一插，就等着找那个理想的干球温差。

We pull out a pocket, we stick it in their turn duct, stick it in a supply duct, and we're looking for a magic dry bulb drop.

每个人都有自己的理想数值。

And everybody's got their magic number.

我听过16度，也听过18度、20度、22度，甚至23度。

I've heard 16, I've heard 18, I've heard twenty, twenty two, 23.

这些都取决于你具体想达成什么目标，非常主观。

All that is very subjective to what you're trying to do.

这仅仅是我们要处理的热量中的一部分。

It's also just one part of the heat that we pull out.

实际上我们面对的是两种热量，但很多人会忽略第二种——如果你在潮湿地区，比如我来自南方，湿度才是最关键的，空调得把空气里的水分除掉。

There's really two kinds of heat that we're having to work with and we forget about the second one, which if you're in any kind of a humid climate, which I'm from the southern climates and humidity is the number one thing, it's the moisture that the unit's gotta pull out.

在潮湿环境下做空调的都知道，一到高温高湿天刚启动时，排水管就像水管一样哗哗流水。

Now any of us who work with air conditioning in the humid environment, we know that because the drain line is like a water hose whenever you start really running it on a very hot humid startup.

我们得把湿气排掉。

We got to remove the moisture.

空调最大的负荷其实是除湿，不是降温。

The number one load on an air conditioning unit is the humidity.

除湿所消耗的能量，比单纯降温还要多。

It takes more to remove the humidity than it does to drop the temperature.

从实际操作来看，我们装好空调，屋里又热又潮，一开机器，客户马上问：‘喂，温度怎么还没降下来？’这时候我们该怎么回答？

Now from a real world standpoint, we'll put in a unit, house will be hot, it'll be humid, and we turn it on, and when the customer says, hey, ho, ho, the temperature, what do we tell them?

等它慢下来，温度才会降下来。

Well, when it slows down, then the temperature come down.

所以我们下意识都知道，得先除湿，才能开始降温。

So we intuitively know we gotta get rid of the humidity before we start dropping temperature.

但我们要怎么知道，除湿的量是不是刚刚好呢？

But how do we measure whether or not we are removing the proper amount of humidity?

那就是湿球温度的下降。

Well that's a wet bulb drop.

干球温度的下降只是其中一部分，说真的，在潮湿地区，这根本不是最重要的部分。

The dry bulb drop is only one part of the equation and believe it or not, it's really not the most important part of the equation if you're in a humid climate.

如果你在像亚利桑那这样的干燥地区，那确实只需要关注干球温度，因为你得往系统里加水，明白吗？

Now if you're in a dry area like Arizona, then all you worry about is dry bulb because you're gonna have to add water to the system, alright.

这就是蒸发冷却器起作用的地方，这种散热方式只在非常干燥的气候里有效。

This is where swamp coolers work and that kind of heat transfer works up in the very dry arid climates.

但我们必须处理湿球温度的问题。

But we gotta deal with that wet bulb.

干球温度反映的是显热，湿球温度才是真正衡量湿度的，也就是潜热。

So dry bulb is moving sensible heat, wet bulb is actually measuring the humidity which is called latent heat.

咱们得去掉的，就是这两种热量。

Those are the two kind of heats we gotta remove.

最关键的是，我们得时刻监控，是不是在最有效地转移热量。

And it's extremely critical that we are monitoring are we transferring the most heat?

接下来咱们聊聊，热量传递到底是怎么回事。

And then now let's get into what heat transfer actually is.

热量传递说白了，就是热量从一个地方传到另一个地方的速度。

Heat transfer is nothing more than how fast we're transferring the heat from one place to the next.

比如，房子的内墙要是没做保温的话。

So for instance, interior walls of a house, they're not insulated.

明白吗？

Okay?

因为热量会在石膏板之间自由传递，直到温度平衡，除非你有特殊需求，想让某个房间保持特定的温湿度条件。

Because the heat transfers between the sheetrock and it equalizes out unless you want to trap a particular room and keep it a certain condition for under special reasons.

但建筑物的外墙是保温的，因为我们不希望热量这么快传进来。

But the outside walls of a structure are insulated because we don't want that heat transfer to come through so fast.

说到热传递，其实分两种情况。

Now when we talk about heat transfer, we got two kinds.

一种是慢的、低效率的热传递，另一种是高效的热传递。

We got it a slow or a low heat transfer and a high heat transfer.

在空调的盘管上——也就是所有热交换发生的地方，特别是蒸发器盘管，我们希望热传递效率越高越好。

When it comes to air conditioning on the coils, which is where all of it takes place, the evaporated coil, we want a high heat transfer rate.

明白吧。

Alright.

我们得让盘管尽可能多地吸收热量。

We wanna really absorb that heat into that coil.

设计时，盘管的表面积、每英寸的翅片数量，还有流过盘管的风量，都很关键。

Now when they're engineered, the surface area of the coil matters, how many fins per inch matters, and how much airflow is going across the coil.

不过我们自己不设计，都是直接用厂家按标准条件预装好的。

Now we don't engineer them, so we get them already prebuilt under design conditions.

所以总热量的计算涉及线圈两侧的焓值变化。

So the total heat formula deals with the enthalpy drop across a coil.

焓值到底是什么？

What is enthalpy?

其实就是进入时的干球温度和湿球温度，跟离开时的干球和湿球温度之间的差别。

That's actually the dry bulb and wet bulb coming in versus the dry bulb and wet bulb coming out.

我们总是很擅长测量干球温度的变化，但湿球温度呢？

We're always good about measuring that dry bulb drop, but what about the wet bulb?

还有就是经过线圈的空气流量。

The other thing is that rate of airflow going across that coil.

在潮湿的环境下，如果风量超过每吨400立方英尺，除湿效果就会变差。

In a humid environment, if you go above 400 CFMs per ton, you're not gonna remove as much humidity.

在干燥的气候里，风量最好超过每吨400立方英尺。

In a dry climate, you wanna do more than 400 CFMs per ton.

很多人会用到450，主要是为了降低干球温度，因为他们根本不用操心湿球温度。

A lot of do four fifty to remove the dry bulb because they don't have any wet bulb to worry about.

但在潮湿的气候下，你必须把湿球温度降下来。

But in a humid climate, you've got to remove the wet bulb.

我来给你举个例子，说明这到底是怎么运作的。

Let me give you an example how this works.

假设桌上有一滩水，你拿一块普通的抹布，而且是干的。

Let's say you got a puddle of water on the table and you got regular dish cloth and it's dry.

如果我拿这块抹布飞快地在桌面上来回擦，它只会吸走一点点水，大部分水反而会被甩出去，因为速度太快，水根本来不及被抹布吸进去。

Now if I take that dish cloth and I rake it super fast across the table, it's gonna absorb a little bit of water, but most of it's gonna kick right off the table because I was going too fast for the water to get absorbed into that rag.

现在，还是同样的水量，同样的抹布，但这次你慢慢拖过去。

Now let's take the same amount of water, the same size dish cloth, and then take it and move it real slow across there.

这时候会发生什么？

What's it gonna do?

水就有足够的时间被抹布吸进去。

It's gonna have time to absorb the water into that dish cloth.

空气流量也是同样的道理。

It's the same thing with airflow.

我们得让空气流速慢下来，好让它在蒸发器盘管里多停留一会儿，吸收更多湿气。

We gotta slow the air down so that it lingers through that evaporator coil to absorb more humidity.

所以这里有个平衡点——不能太慢，不然盘管会结冰，但最低可以降到每吨350立方英尺，这样能更好地除湿，提升除湿能力。

So this is where we kinda come around, you can't go too low because then we start freezing the coil up, but we can go as low as three fifty CFM per ton to get more moisture out of the air and that's increasing the latent capacity.

通常我们把风量控制在每吨350到450立方英尺之间，中间值400立方英尺每吨是行业标准测试用的风量。

So we have a range from three fifty to four fifty in the middle ground is 400 CFM per ton which is where we do all our capacity ratings at.

这里说的可是实际风量，不是标准状态下的风量。

And it's actual CFM not standard CFM.

不管你在哪儿，这个范围都是适用的。

So we are looking at no matter where you are, that's where we fall.

还有一个关键点，你得看干球温度和湿球温度在通过盘管时各降了多少。

And one of the big key concepts is what are we looking for on a dry bulb and wet bulb drop across a coal?

我跟你们说个不太为人所知的小窍门，好吧？

And I'll tell you this, now this is a little known secret, okay?

大家都凑近点，我要压低声音说，听好了。

So everybody come real close because I'm gonna say it very, very quietly, okay?

有人在看吧？

Somebody's looking, right?

你们都没在看吗？

You guys aren't looking?

好了，小声点，别让别人知道这个秘密，不然这儿所有人的营销套路都要崩了，明白吗？

Okay, shh, don't tell everybody this secret, because if this secret gets out, it's gonna destroy everybody's marketing around here, okay?

在拆掉所有有问题的设备之前，你们只要做个检查就能知道，设备是不是真的在额定容量下运行——不管是两吨还是两百吨，我们说的是风冷蒸发器，对吧？

Now, so before you pull out all the bad gear, all you got to do to see if you're really running the right capacity, I mean like dead on, whether it's a two ton or the 200 ton, and we're talking about air cooled evaporator, right?

还没说到水冷的情况。

We're not talking about water yet.

如果你测出干球温度下降了16到18度，咱们一直都在追求这个数值，别搞到20度，就保持16到18度，同时湿球温度下降10度。

If you measure a 16 to 18 degree dry bulb, we've all been trying to get that number forever, don't go twenty, sixteen to 18 dry bulb along with a 10 degree wet bulb drop.

这才是关键。

This is the critical part.

我们要保持这个比例。

It's a we wanna keep that ratio.

干球16到18度，湿球降10度。

16 to 18 dry bulb with a 10 degree wet bulb.

要是蒸发器两端的温差能达到这两个数值，你知道意味着什么吗？

If you get those two drops across the evaporator, guess what?

那就说明风量是对的。

You got the right airflow.

热交换也正好。

You got the right heat transfer.

制冷剂充注量也刚好。

The system's charged correctly.

搞定啦。

You're done.

好了，再见。

Bye, see you.

一切就都结束了。

It's all over.

好的。

Okay.

这说明蒸发器上的制冷量是符合设计要求的。

That will tell you that at the coil, you're overall getting the right capacity that it was designed to get.

不过我这里说的不是空气分布，不代表空气分配得没问题，明白吗？

Now I'm not talking about air distribution, that doesn't mean it's distributing it properly, okay?

但它能证明你通过蒸发器的风量是正确的，热交换也到位了，根本不用掏出压力表。

But that does tell you that you have the right flow rate across the coil, you got the right heat transfer, and you don't have to pull out your gauges.

最不该做的就是一上来就给设备接压力表。

The last thing you wanna do is put gauges on the equipment.

别一上来就用压力表，要放在最后再用，知道吗？

Don't throw those on first, throw those on last, all right?

咱们来实际测一下。

Let's do some measurements.

我为Carry和Train做现场服务差不多十五年了，期间处理过数百台性能不达标的设备。

I've been a field service rep for Carry and Train for almost fifteen years between the two and I went to hundreds of pieces of equipment that wasn't keeping up.

它根本降不下温度。

It wasn't getting the temperature down.

客户不满意，我们就不停地加制冷剂、放制冷剂，还瞎调整风量。

The customer wasn't satisfied And we're pulling out charge and adding in charge and playing around with the airflow.

事情变得特别乱，明白吗？

It got crazy, okay?

所以记住 insanity 的定义。

So remember the definition of insanity.

一遍又一遍做同样的事，却指望得到不同的结果。

You're doing the same thing over and over and looking for different results.

所以一旦出现这种情况，他们就会找我来处理，明白吗？

So I get called out when insanity kicked in, all right?

我一到现场，碰任何东西之前，不查制冷剂、不测过冷度，先说咱们先测一下机组的湿球和干球温差。

So I'd go out there and before we touched anything, before we checked charge, sub cooling, all that stuff, I said let's do a wet bulb and dry bulb drop across the unit.

得跑到机组那儿去测，别在出风口那儿看，必须到机组所在的位置。我进过太多太多太热的阁楼了，对吧？

So we got to get where the unit is, don't check it at the vents, got to get to where the unit is and I've been into lots and lots and lots of hot, hot, hot attics, right?

我们会测量蒸发器盘管两侧的温差。

And we would measure the drop across the coil.

如果干球温度是16到18度，湿球温度是10度，那我们就得离开设备，重新考虑别的原因。

If I'm getting 16 to 18 dry bulb with a 10 wet bulb, we're stepping away from the equipment.

设备本身是没问题的。

The equipment itself is okay.

可能是风管分布有问题，也可能是系统过载，或者有其他因素，甚至可能是因为室外温度高达105度，而设备只设计用于95度的环境。

It may be a duct distribution issue, it may be overloaded, there's other things happening or it could be that it's 105 degrees outside and it's designed for 95 outside.

所以一旦室外温度超过95度，设备就扛不住了，因为它已经超出了额定能力。

That's why a unit cannot keep up when you get above 95 outside, you start going above its rated capacity.

如果设备选得太大，那又是另一个问题了。

Now if they're oversized, whole another problem right there.

归根结底，这些简单的数据就能说明问题。

So you can boil it down to those simple numbers.

既然我们知道了标准值，那当实际情况不符时，我们该怎么做？

Now once we know the standard, what do we do when it's not that way?

这是有问题，还是正常情况？

Is it bad or is it okay?

咱们来分析一下。

Well, let's think about it.

如果是在高温高湿环境下启动，屋里温度85度，相对湿度75%，对吧？

If you're doing a hot startup and it's humid in the house, let's say it's 85 in the house and it's 65, 75% relative humidity, right?

又热又潮。

Hot and humid.

这时候湿球温差会更大，因为你还得除湿，对吧？

Well then you can expect the wet bulb drop to be greater because we're now we got to get rid of the humidity, right?

所以我们现在可能看到的是——我随便举个例子——在设计条件下，干球温度16到18度，湿球温差10度，但现在情况不一样了。

So now we're looking for maybe it's gonna be, I'm just picking some numbers, but remember the standard is 16 to 18 dry bulb at a 10 degree wet bulb under design conditions.

正常情况是室内80度，相对湿度50%，室外95度。

So we'll be running it 80 degrees indoor, 50% relative humidity, 95 outside.

但如果湿度升到65%，湿球温度会更高，干球温度会更低，这其实完全正常。

Well, if we're out of those parameters and let's say we're 65% relative humidity, you're going to expect the wet bulb to be greater and the dry bulb to be less, and you're okay.

但如果不是这样，那就有问题了。

Now, if it's not that way, now we got a problem.

如果干球温降和湿球温降都很低，大概率是制冷量不足，明白吗？

If we're running a low dry bulb drop and a low wet bulb drop, probably a capacity issue, all right?

这要么是制冷剂充注量不对，要么是节流装置出了问题，得去检查一下。

And it's gonna be either a refrigerant charge or a metering device issue, and you gotta go check that.

如果湿球温降特别高，但干球温降很低，那多半是湿度太大，得想办法除湿。

If we're running a very high wet bulb drop, but a low dry bulb, chances are you're just fighting a lot of humidity and you got to get that out.

在动手用各种诊断工具之前，先做这几个简单的检查，能帮你快速定位问题，好吗？

These are some good basic quick checks before you start pulling out all the diagnostics tools to figure out where the problem is, okay?

除了气流之外，还有另一个影响换热的因素，因为我特别看重空气流通。

Now the other thing that's going to affect your heat transfer other than airflow because I'm a big airhead here.

没错，气流不足确实会出问题。

So yes, low airflow can be a problem.

气流太低的话，肯定会有问题。

Too low airflow would definitely be a problem.

但记住，我们通常能控制在350到450之间，具体要看我们想达到什么效果。

But remember, we can get between three fifty and four fifty depending on what we're trying to achieve.

低风量是个问题，但还有什么别的因素会阻碍我们需要的热交换呢？

So low airflow, but what else can hinder the heat transfer that we need to get?

之前我们讲过，蒸发器线圈积灰会严重影响热交换效率。

Well, we've talked about it before, talking about dirty evaporator coils, that's gonna drop the heat transfer rate going through there.

还有就是滤网脏了也会有影响。

We're also looking at dirty filters.

别忘了风机叶轮也脏，而且得两面都清理干净。

Don't forget dirty blower wheels and it's gotta be both sides.

得把风机外壳拆下来，彻底拆开，把叶轮两面都清干净。

We gotta pull out the blower housing, we gotta pull that blower housing apart and clean both sides of that blower wheel.

记住，那些叶片都是小小的叶片，像小勺子一样。

Remember, they're little bitty scoops, little bitty scoops.

如果一半的叶片都被灰尘堵死了，你只清理了看得见的那一面，另一半没动，相信我，我太懂了，我以前也这么干过——另一面也必须彻底清干净。

And if you get half that scoop all compacted with dirt, you don't get it out of there, and you only clean the half the wheel that we can see, trust me, I know, I've been there, alright, we gotta get the other side clean.

现在我们要确保气流的量是正确的。

Now we're gonna move the correct amount of airflow.

这在热传递过程中非常重要。

That is very important when it comes to heat transfer.

但别忘了，冷凝式燃气炉的二级热交换器呢？

But also, what about the secondary heat exchanger in a condensing gas furnace?

别忘了，夏天它也会阻碍热传递。

Don't forget, that's in play to slow down heat transfer in the summertime.

它也会积灰。

It can get dirty.

很多情况下，夏天运行时我们根本不会想到燃气炉内部。

And a lot of times we don't even think about the inside of a gas furnace when we're operating in the summertime.

我们只关注燃气炉送风侧的蒸发器盘管。

We're looking at evaporator coil on the supply side of the gas furnace.

我们会把风机拆下来，往里看，检查那个二级热交换器。

We'll pull the blower and look up in there and look at that secondary heat exchanger.

就在那儿，看看是不是需要刷一刷。

It's right there and see if it needs to be brushed off.

别往上面喷清洗剂。

Don't spray coil cleaner on the darn thing.

用刷子清理一下，再用吸尘器吸干净，把灰尘松掉，这可能是问题所在。

But brush it off, shop vac it, get it loose, that may be an issue.

它可能会被压实，这跟回风管道里的状况、我们吸入回风的东西以及吹向线圈的气流都有关系。

It can be compacted depending on what's happening in the return line and what we're sucking into the return and blowing it into the coil.

明白吗？

Okay?

所以，这也是你在考虑热交换时要注意的另一点。

So that's the other thing that you wanna look at for heat transfer.

把这些都检查一遍之后，你就能清楚地判断出该怎么调整了。

When you get all that together, you're gonna be able to actually see where you need to place it one way or the other.

因为一旦设备开始运行，问题可不总是制冷剂不足那么简单。

Because once we get the unit running, it's not always just low charge.

另外还要记住，这可能是多种因素累积的结果。

And remember also, it can be a cumulative effect.

制冷剂可能稍微不足，还没严重到让过冷度明显异常，也没让过热度表现得很糟糕。

It may be slightly low, not enough to show up maybe on sub cooling too bad, maybe not enough to show up on super heat too bad.

但如果制冷剂略少、风量不足、线圈又有点脏，这些因素加在一起就出问题了。

But if it's slightly low on charge, slightly low on airflow, slightly dirty coils, now all that's gonna add up.

这时候，设备的性能就开始下降了。

Now we're gonna start losing performance.

那你怎么知道自己的设备性能在下降呢？

And again, how can you know if you're losing performance?

去测量一下线圈两侧的干球温度和湿球温度差。

Go and do that dry bulb, wet bulb drop across the coil.

别忘了同时测湿球温度，明白吗？

Just be sure to do the wet bulb along with it, okay?

那这种情况只适用于空调吗？

Now does this apply to anything other than just air conditioning?

没错。

Absolutely.

我们换个角度，聊聊制热的情况。

Let's flip it around and let's talk about heating.

制热时的风量要好一些。

The heating airflow is a little bit better.

全是显热。

It's all sensible.

只涉及干球温度。

It's nothing but dry bulb.

这时候你最容易拿到准确的读数。

This is where you can really get some really good readings.

比如说，我们只看制热侧时，怎么判断风量是否合适？

So for instance, how do we know we've got a good CFM reading when we're just doing the heating side?

如果是电加热丝，可以用温升法来测算。

Well, with heat strips, you can do the temperature rise method.

你可以在这里测电压、电流，换算成瓦数，再用显热公式算出通过加热丝的风量。

It's where you can pull the volts, you can pull the amps, you convert it to watts, and then you're gonna use the sensible heat formula to get airflow across the heat strips.

但别忘了，把温度探头移出加热丝的直视范围。

But just remember, get your temperature probe out of the line of sight of the heat strips.

尽量绕到靠近加热丝的角落，但别让探头直接对着加热丝散发的辐射热。

So go around the corner as close as you can to them but just don't let that temperature probe see the radiant heat coming off those heat strips.

有些温度探头自带遮挡罩，那样你就可以直接放在前面了。

Now there are some temperature probes that have a shield that you can use and then you can get right in front of them.

不过即便有遮挡罩，最好还是稍微离远一点；要是有罩子，那就没问题了。

But you wanna get a little bit away anyway, but if you got a shield, you're in good shape.

如果没有遮挡罩，那就尽量靠近，但千万别让探头正对着加热丝，明白吗？

But if you don't, just get as close as you can without being in line of sight, all right?

一旦测出风量，你就能判断实际输出的BTU是否达标了，因为你现在有显热公式可用。

So once we get, we can use that to measure the airflow, then you can actually see if you're getting the correct BTUs as well, because now you got the sensible heat formula.

当你需要输送大量显热时，所需的风量也会发生变化。

When you're looking at trying to move a lot of sensible heat, the CFM requirement changes.

那到了燃气炉这边，我们最明显的判断依据是什么？就是风量不足或者风量过大。

So when we got to gas furnaces, what's one of our biggest indicator that we don't have either enough airflow or we got too much airflow?

那就是温升，对吧？

And that's your temperature rise, right?

我们经常忽略燃气炉上一个特别关键的测量指标，就是温升范围。

If there's one beautiful thing to measure that we forget all the time on gas furnaces, it's measure the temperature rise range.

这个温升其实直接告诉你，空气从回风口进入送风口之后，被增加了多少显热。

And that's really telling you that sensible heat that you're adding to the air once it comes from the return into the supply.

如果你看燃气炉的温升数据，发现它在参数表上已经跑到极限位置了。

So if you look at the gas furnace and the temperature rise, and let's say you look at the range and it's all the way out there on the data table.

别急着走开，我知道你们平时用什么方法。

Don't walk away because I know what we're using.

你们最爱用的那个工具。

We're using our favorite tool.

你们最爱用的那个工具——手摸感受法，对吧？

We're using our favorite tool, the handometer, right?

这个手测仪挺管用的。

The handometer is great.

这就是我们的手测仪，明白吧？

So here's our handometer, all right?

手测仪里头带了个温度探头，显示要么热，要么温，要么不太热。

We got a temperature probe built into our handometer and it either says hot, warm or not so warm.

这都是手测仪给的读数，对吧？

That's our handometer readings, right?

我们把手测仪放到出风口一放，哎，这风挺热的。

And so we put our handometer over the vent, we go, oh, that's hot air.

没问题了，对吧？

Good to go, right?

完了，就这么点测量工作。

And we're done, that's all our measurements.

可别这么干，行吗？

Don't do that, right?

我可以告诉你，我做过很多次了，这样做不对。

I can tell you, I've done it plenty of times and it's not right.

如果你去看温升范围，比如说40到70，这意味着燃气炉的最小温升，你得在炉子上测，别急着在回风口和送风口之间比。

If you go look at the temperature rise range, let's say it's 40 to 70, what you want to do is that's telling you that the minimum temperature rise through that gas furnace and you want to measure it at the furnace, don't measure it at the return versus supply yet.

要是有时间，我还能告诉你怎么用这个快速诊断风管漏风，特别快，明白吗？

We had time, I could tell you how to use that to diagnose duct leakage pretty darn fast, all right?

但现在我们还在设备这边。

But right now we're at the equipment.

比如说温升标的是40到70，那就意味着我们至少要达到40的温升。

If it says 40 to 70 rise as an example, that means the minimum rise we wanna get is 40.

在这种情况下，最高温升是70。

The maximum rise is 70 in this case.

但我们别一上来就冲着最低或最高值去，得找中间值。

But we don't wanna start out at the lowest or the highest, we wanna be in the middle.

所以你要算一下40和70之间的差值，中间值就是15度。

So you wanna take the difference between forty and seventy in this case, which is the middle is 15 degrees.

所以我们往上走，在这种情况下，温升大约是55度。

So we're gonna go up, so in this case we'd be about a 55 degree rise.

如果温升落在这个区间中间，那就说明风量合适，燃气量也正好。

If we got in the middle of that range, that means our airflow's good, that means our gas charge is good.

热交换的输出是符合要求的。

We're producing the right amount of heat transfer.

但这并不意味着房子能保持舒适，因为炉子处理的是回风管里传来的空气温度。

Now, that doesn't mean that the house is still gonna maintain because that furnace is working on whatever temperature's coming down that return line.

我曾经遇到一个案例，回风管有一段长达15英尺的直管，结果进入炉子的空气比室内还低了10度。

I've had a job where I've had a 15 foot of one piece of ductwork and we were 10 degrees colder entering the furnace than it was in the house.

原因就是回风箱的某个位置有缝隙，没密封好。

And it's all because one part of the pan for the return had a gap and it wasn't sealed.

晚上它会吸进大约28度的冷空气，导致进入炉子的回风温度大幅下降。

And it was sucking in at night about 28 degree air dropping the return air temperature entering to the furnace.

炉子本身其实是在正常工作的。

The furnace was doing its job.

温度上升完全正常，但它根本不是在根据室内温度工作。

It was dead on, but it wasn't working on house temperature.

它是在根据周边环境的温度工作。

It was working on the neighborhood temperature.

它其实是在根据地下室的温度工作。

It was working on the crawl space.

所以你得留意这些细节。

So you gotta look at those kind of things.

但温升能告诉你，这台燃气炉是不是在正常工作。

But the temperature rise will tell you if that gas furnace is doing its job.

我举个例子，有次有人找我，说他的燃气炉怎么也升不到35度以上，急得不行。

Now I'll give you an example, I had a gas furnace that a guy called me on and he could not get it above a 35 degree temperature rise to save his life.

其中一个办法是，如果温升太低，就减缓风量。

Now one of the tricks is if it's too low a temperature rise, then slow the airflow down.

这样能让空气有足够时间接触热交换器，吸收更多热量，提高热传递效率，温度也就上去了。

That gives the air time to warm up to that heat exchanger, absorb more heat out of that heat exchanger, rate of heat transfer and get hotter.

如果热传递太高，那就加快风速。

Or if it's too high of a heat transfer, then you're going to speed the air up.

所以如果你的温升接近70度甚至更高，就得加快风速来降温。

So if you're running on the high end of that temperature range, say you're running up close to 70 above or higher, then you're gonna speed up the air to cool it down.

空气流经热交换器的速度越慢，温升就越大。

So if it's going slow through the heat exchanger, you're gonna get a big temperature rise.

如果流得太快，温升就会降低。

If it's going real fast, it's gonna lower the temperature rise.

所以调节的就是这个原理。

So that's how you're gonna play with it.

他怎么弄都没用。

He couldn't get it to do anything.

我们过去一看，记得燃气炉和燃气机组，过去二十五年左右都装了诱导排风电机。

So we go there, and remember gas furnaces, gas packs, we now have these draft inducing motors for the last twenty five years or so.

燃烧器看起来很漂亮，对吧？

And the burners look beautiful, okay?

是喷射式燃烧器。

In shot burners.

对吧？

Right?

看起来像喷气发动机。

It looks like a jet.

很漂亮。

Beautiful.

我就问他，你检查过燃气压力了吗？

So I asked him, I said, did you check the gas pressure?

他说没有。

He goes, no.

他说火焰看起来挺正常的。

He said, the flames look good.

我就是随便调调空气流量。

I'm just messing around with the airflow.

我说，咱们还是把燃气压力检查一下吧。

I said, well, let's just check the gas pressure.

先把这事确认了再说。

Let's just get that out of the way.

要不是我亲眼看到，我真不敢相信那个读数。

Now I would not have believed the reading we saw if I hadn't seen it myself.

again，一切看起来都完美无瑕。

Again, everything looked beautiful.

听起来也特别棒。

It sound beautiful.

顺便说一下，那个测压计显示一切正常。

By the way, the handometer said everything was perfect.

根据我那个97度的测温计，从通风口吹出来的是热风，明白吗？

It was hot air come out of the vents according to my 97 degree handometer, alright?

但温度上升就是达不到应有的水平。

But it wasn't getting the right temperature rise.

燃气压力，也就是集气管的燃气压力，我说真的，只有0.9英寸水柱。

The gas pressure, the manifold gas pressure, I kid you not, was point nine.

正常应该达到3.5英寸水柱才对。

It needed to be 3.5 inches of water gum.

结果呢，就只有0.9英寸水柱。

It was point nine.

我们从燃气表到燃气设备之间，管道总共也就十英尺长。

And all it was, we had like only about 10 feet of gas pipe from the meter to the gas pack.

但他们留下了一小段旧管道，以为是个带堵头的T形接头。

But they left one little original section, which they thought was a t with a plug in it.

其实那是老式的截止阀，一个燃气旋塞，而且是斜着装的，呈45度角。

That was an old shut off valve, old gas cock, and it was at a 45 degree angle.

等我们彻底打开它之后，燃气才终于能完全通到计量表。

When we open that up all the way, we got full flow of gas to the gas meter.

马上，压力就升到了3.3英寸水柱。

Immediately, we got a 3.3 inches of water column.

五分钟内，我们的温升就稳定了。

Within five minutes, our temperature rise was dead metal.

运行得特别顺畅。

Worked like a champ.

明白吗？

K?

所以这是检查燃气炉时另一件要注意的事。

So that's the other thing you wanna check on a gas furnace.

这里有个关于燃气炉的小提示。

There's a little gas furnace note here.

检查一下温升情况。

Check the temperature rise.

如果温升正常，那就完美了。

And if you're getting the temperature rise, kinda golden.

好了吧？

Alright?