A survey shows 87% of domestic households have had air conditioners since 2005.
You can scarcely imagine shopping malls without air conditioning systems.
Amongst the heating, ventilation, and air conditioning (HVAC) systems for commercial buildings, gas-powered air conditioners account for a large portion.
The principle is similar to conventional car air conditioners. The basis is a gas engine and an industrial compressor that compresses/expands the coolant gas to heat or cool the air.
This type of unit is referred to as a gas engine driven heat-pump air conditioner, or, in short form, gas heat pump or GHP.
The advantages of gas-powered air conditioners include, in summer, no usage of peak electricity, and in winter, use of waste heat for efficient heating.
They have less impact on the environment because of low operating costs and lower carbon dioxide emissions.
Aisin Seiki is one of the big four GHP manufacturers on the planet, with a market share of approximately 23%, the third largest as of 2005.
Since Aisin Seiki first entered the market in 1987 with a GHP system co-developed with Tokyo Gas, the product segment has grown into one of the main pillars of the company’s energy business.
However, this market presence was not built in a day.
There is a long story behind Aisin's GHPs, how engineers resolved what was thought practically impossible in the industry to get out of the worst.
Gas Heat Pump (GHP) Air-conditioning System
The gas engine powers the compressor that circulates the coolant. The coolant circulates in the gaseous or liquid state delivering cold and heat.
“Can you sit right here and have a bowl of ramen?”
Sweating all over in a small ramen shop at well over 40˚C, an Aisin GHP service tech just kept eating the noodles in the bowl without a word of reply to the shop owner.
That was not a single case. Voices of anger were hurled at every service tech who visited customers to repair failed GHPs.
Rages occasionally escalated to the degree that some customers threw a plate of fried noodles or detergent, while others locked up service personnel in warehouses or on rooftops.
The malfunctions were found and reported between 1987 and 1990.
Joint development on a new GHP system started with Tokyo Gas in 1985.
The initial project offer came from the gas company, in search for a way to boost natural gas consumption.
In 1987, a GHP boasting a 7.5 hp unheralded by any company came out from the project. In the third year from the kickoff, annual sales from the model posted 3.2 billion yen.
No one knew the project was on the verge of going to hell.
Soon, reports of troubled GHPs came in one after another.
Before the cause of failure was identified, another malfunction occurred, and that lasted for months. The Development Dept. panicked.
Having to respond to repairs, the Customer Service Dept. got short-staffed.
It didn't take long before Aisin was disgraced as “the company of malfunctioning GHPs.”
Customer Service personnel shared the belief: “what we need to do here is to report detailed, accurate trouble information from each site to the Development Dept.”
Also needed was patience to deal with being humiliated.
The biggest problem was frequent breakdowns of the compressors.
The cause turned out to be that they were not designed durable enough to last the product lifetime taking into account the long operation times and extended length of piping particular to GHPs.
The design life should be improved up to 20,000 hours without wasting a second.
The person in charge of product development visited the manufacturer of the compressor.
He was greeted with a cold response, “A service-life of 20,000 hours under such harsh conditions is something we can never offer. You should come up with any good ideas of your own that make it possible.”
The members heard people say things like, “It's just thoughtless to give it a try,” or “Aisin is big enough to spend time and money on a hobby.”
They made a decision.
“We are gonna redo everything from scratch.”
Disassembled compressors that had failed revealed that the refrigerating machine oil had failed to return to the compressors.
If it had been a car air conditioner, the length of compressor circuit piping would have been as short as 2-3 m. For a GHP, the length can increase to 100 m or more.
The longer the piping, the more oil remains in the piping, causing less amount to return to the compressor.
First needed was to determine the returning amount of oil.
That was easier said than done.
Refrigerating machine oil flows through the piping together with the coolant, but some of this coolant mixes in with the oil. In some cases, more than 50% of the resultant liquid is coolant.
For car air conditioners, the concentration of oil constituents can be determined by simple methods, but they are unsuitable for GHPs.
“How can the percentage of the coolant that mixes in with the refrigerant oil be determined?”
There existed no instruments capable of measuring that.
Even worse, no method that could reliably measure the soluble constituents had been established.
It was the theory behind oil-gas separators that caught the eye of one product engineer trying to solve the problem.
“An oil-gas separator, if measuring accuracy were enhanced, could quantitatively measure how much oil in the gas mixture returns to the compressor,” he thought.
The idea worked and brought a breakthrough to the project.
Available for the first time in the industry, the method and device for quantitatively measuring oil return significantly contributed to more durable GHPs.