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# The use of heat pumps has been held back largely by skeptic

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The use of heat pumps has been held back largely by skeptic [#permalink]  22 Jun 2019, 11:57
Expert's post
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Question Stats:

15% (04:28) correct 84% (10:50) wrong based on 13 sessions
The use of heat pumps has been held back largely by skepticism about advertisers' claims that heat pumps can provide as many as two units of thermal energy for each unit of electrical energy used, thus apparently contradicting the principle of energy conservation.

Heat pumps circulate a fluid refrigerant that cycles alternatively from its liquid phase to its vapor phase in a closed loop. The refrigerant, starting as a low-temperature, low-pressure vapor, enters a compressor driven by an electric motor. The refrigerant leaves the compressor as a hot, dense vapor and flows through a heat exchanger called the condenser, which transfers heat from the refrigerant to a body of air. Now the refrigerant, as a high-pressure, cooled liquid, confronts a flow restriction which causes the pressure to drop. As the pressure falls, the refrigerant expands and partially vaporizes, becoming chilled. It then passes through a second heat exchanger, the evaporator, which transfers heat from the air to the refrigerant, reducing the temperature of this second body of air. Of the two heat exchangers, one is located inside, and the other one outside the house, so each is in contact with a different body of air: room air and outside air, respectively.

The flow direction of refrigerant through a heat pump is controlled by valves. When the refrigerant flow is reversed, the heat exchangers switch function. This flow-reversal capability allows heat pumps either to heat or cool room air.

Now, if under certain conditions a heat pump puts out more thermal energy than it consumes in electrical energy, has the law of energy conservation been challenged? No, not even remotely: the additional input of thermal energy into the circulating refrigerant via the evaporator accounts for the difference in the energy equation.

Unfortunately, there is one real problem. The heating capacity of a heat pump decreases as the outdoor temperature falls. The drop in capacity is caused by the lessening amount of refrigerant mass moved through the compressor at one time. The heating capacity is proportional to this mass flow rate: the less the mass of refrigerant being compressed, the less the thermal load it can transfer through the heat-pump cycle. The volume flow rate of refrigerant vapor through the single-speed rotary compressor used in heat pumps is approximately constant. But cold refrigerant vapor entering a compressor is at a lower pressure than warmer vapor. Therefore, the mass of cold refrigerant --- and thus the thermal energy it carries --- is less than if the refrigerant vapor were warmer before compression.

Here, then, lies a genuine drawback of heat pumps: in extremely cold climates-where the most heat is needed-heat pumps are least able to supply enough heat.
17. The primary purpose of the passage is to

(A) explain the differences in the working of a heat pump when the outdoor temperature changes
(B) contrast the heating and the cooling modes of heat pumps
(C) describe heat pumps, their use, and factors affecting their use
(E) expose extravagant claims about heat pumps as false

[Reveal] Spoiler: OA
C

18. The author resolves the question of whether heat pumps run counter to the principle of energy conservation by

(A) carefully qualifying the meaning of that principle
(B) pointing out a factual error in the statement that gives rise to this question
(D) denying the relevance of that principle to heat pumps
(E) explaining that heat pumps can cool, as well as heat, room air

[Reveal] Spoiler: OA
C

19. It can be inferred from the passage that, in the course of a heating season, the heating capacity of a heat pump is greatest when

(A) heating is least essential
(B) electricity rates are lowest
(C) its compressor runs the fastest
(E) the heating demand surges

[Reveal] Spoiler: OA
A

20. If the author's assessment of the use of heat pumps is correct, which of the following best expresses the lesson that advertisers should learn from this case?

(A) Do not make exaggerated claims about the products you are trying to promote.
(C) Do not use facts in your advertising that will strain the prospective client's ability to believe.
(D) Do not assume in your advertising that the prospective clients know even the most elementary scientific principles.
(E) Concentrate your advertising firmly on financially relevant issues such as price discounts and efficiency of operation.

[Reveal] Spoiler: OA
C

21. The passage suggests that heat pumps would be used more widely if

(A) they could also be used as air conditioners
(B) they could be moved around to supply heat where it is most needed
(C) their heat output could be thermostatically controlled
(D) models with truly superior cooling capacity were advertised more effectively
(E) people appreciated the role of the evaporator in the energy equation

[Reveal] Spoiler: OA
E

22. According to the passage, the role of the flow restriction in a heat pump is to

(A) measure accurately the flow rate of the refrigerant mass at that point
(B) compress and heat the refrigerant vapor
(C) bring about the evaporation and cooling of refrigerant
(D) exchange heat between the refrigerant and the air at that point
(E) reverse the direction of refrigerant flow when needed

[Reveal] Spoiler: OA
C

23. The author regards the notion that heat pumps have a genuine drawback as a

(A) cause for regret
(B) sign of premature defeatism
(C) welcome challenge
(D) case of sloppy thinking
(E) focus for an educational campaign

[Reveal] Spoiler: OA
A

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Re: The use of heat pumps has been held back largely by skeptic [#permalink]  23 Jun 2019, 08:07
Can anyone explain 21st? I thought B...
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Re: The use of heat pumps has been held back largely by skeptic [#permalink]  23 Jun 2019, 11:34
Expert's post
the first sentence clearly states

The use of heat pumps has been held back largely by skepticism about advertisers' claims that heat pumps can provide as many as two units of thermal energy for each unit of electrical energy used, thus apparently contradicting the principle of energy conservation.

To explain this apparent paradox the operation of the heat pump is explained. Moreover, is also explained some drawbacks when the temperature of the outside is too cold.

Also, the third paragraph says

The flow direction of refrigerant through a heat pump is controlled by valves. When the refrigerant flow is reversed, the heat exchangers switch function. This flow-reversal capability allows heat pumps either to heat or cool room air.

Which means we do have a full explanation how it operates.

No contrast is showed along the entire passage.

Regards
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Re: The use of heat pumps has been held back largely by skeptic [#permalink]  22 Jan 2020, 15:02
To answer question 21, this is the parts that you need to read - the correct answer is E
Quote:
The use of heat pumps has been held back largely by skepticism about advertisers' claims that heat pumps can provide as many as two units of thermal energy for each unit of electrical energy used, thus apparently contradicting the principle of energy conservation.

The above excerpt shows the main problem the whole passage and that was because of the claim that advertisers had made - "1 electrical energy unit = 2+ thermal energy"
Quote:
No, not even remotely: the additional input of thermal energy into the circulating refrigerant via the evaporator accounts for the difference in the energy equation.

The above excerpt answers the problem. Because of the role of the evaporator, it all makes sense that advertisers claimed that way. So if people understand this role, heat pumps would have been used more widely
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Re: The use of heat pumps has been held back largely by skeptic [#permalink]  22 Jan 2020, 15:03
Carcass wrote:
the first sentence clearly states

The use of heat pumps has been held back largely by skepticism about advertisers' claims that heat pumps can provide as many as two units of thermal energy for each unit of electrical energy used, thus apparently contradicting the principle of energy conservation.

To explain this apparent paradox the operation of the heat pump is explained. Moreover, is also explained some drawback when the temperature of the outside is too cold.

Also, the third paragraph says

The flow direction of refrigerant through a heat pump is controlled by valves. When the refrigerant flow is reversed, the heat exchangers switch function. This flow-reversal capability allows heat pumps either to heat or cool room air.

Which means we do have a full explanation how it operates.

No contrast is showed along the entire passage.

Regards

I think the official answer is E
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Re: The use of heat pumps has been held back largely by skeptic [#permalink]  22 Jan 2020, 15:07
Can someone explain 23? if you can point out where to look at the author's opinion, that'll be great
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Re: The use of heat pumps has been held back largely by skeptic [#permalink]  22 Jan 2020, 16:02
mind wrote:
Can someone explain 23? if you can point out where to look at the author's opinion, that'll be great

The final paragraph of the passage.

Here, then, lies a genuine drawback of heat pumps: in extremely cold climates-where the most heat is needed-heat pumps are least able to supply enough heat.
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Re: The use of heat pumps has been held back largely by skeptic [#permalink]  22 Jan 2020, 18:18
theBrahmaTiger wrote:
mind wrote:
Can someone explain 23? if you can point out where to look at the author's opinion, that'll be great

The final paragraph of the passage.

Here, then, lies a genuine drawback of heat pumps: in extremely cold climates-where the most heat is needed-heat pumps are least able to supply enough heat.

Why would it be a cause for regret though. Reading the final paragraph, it does not seem like he regrets anything. There may be some connections with other paragraphs that I may have missed
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Re: The use of heat pumps has been held back largely by skeptic [#permalink]  22 Jan 2020, 18:37
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mind wrote:
theBrahmaTiger wrote:
mind wrote:
Can someone explain 23? if you can point out where to look at the author's opinion, that'll be great

The final paragraph of the passage.

Here, then, lies a genuine drawback of heat pumps: in extremely cold climates-where the most heat is needed-heat pumps are least able to supply enough heat.

Why would it be a cause for regret though. Reading the final paragraph, it does not seem like he regrets anything. There may be some connections with other paragraphs that I may have missed

Coz In the previous paragraph, the author began by saying "Unfortunately, there is one real problem..."

Hope that helps.
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Re: The use of heat pumps has been held back largely by skeptic [#permalink]  24 Jan 2020, 20:16
Oh I see now, thank you
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Re: The use of heat pumps has been held back largely by skeptic [#permalink]  12 Feb 2020, 16:33
Could some one help with Q 18, Q19 & Q20:

Q.18. When I attempted it, I went for option B. - understanding that the statement was incorrect as it missed certain facts, hence went for "factual error"

Q.19. For which part of the passage can this be inferred ?

Q.20. If the author's assessment of the use of heat pumps is correct, which of the following best expresses the lesson that advertisers should learn from this case?
Is option (C) right (and option - D wrong) because the skepticism about heat pumps was not brought about by lack of knowledge of prospective clients but rather awareness of all the facts and details ? Thus, one should be careful in exposing only certain facts - without revealing the entire story
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Re: The use of heat pumps has been held back largely by skeptic [#permalink]  13 Feb 2020, 13:56
Expert's post
mind wrote:
Carcass wrote:
the first sentence clearly states

The use of heat pumps has been held back largely by skepticism about advertisers' claims that heat pumps can provide as many as two units of thermal energy for each unit of electrical energy used, thus apparently contradicting the principle of energy conservation.

To explain this apparent paradox the operation of the heat pump is explained. Moreover, is also explained some drawback when the temperature of the outside is too cold.

Also, the third paragraph says

The flow direction of refrigerant through a heat pump is controlled by valves. When the refrigerant flow is reversed, the heat exchangers switch function. This flow-reversal capability allows heat pumps either to heat or cool room air.

Which means we do have a full explanation how it operates.

No contrast is showed along the entire passage.

Regards

I think the official answer is E

Sorry I typed C for wrong. I meant E
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Re: The use of heat pumps has been held back largely by skeptic [#permalink]  13 Feb 2020, 14:27
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18. The author resolves the question of whether heat pumps run counter to the principle of energy conservation by

(A) carefully qualifying the meaning of that principle
(B) pointing out a factual error in the statement that gives rise to this question
(D) denying the relevance of that principle to heat pumps
(E) explaining that heat pumps can cool, as well as heat, room air

Quote:
Heat pumps circulate a fluid refrigerant that cycles alternatively from its liquid phase to its vapor phase in a closed loop. The refrigerant, starting as a low-temperature, low-pressure vapor, enters a compressor driven by an electric motor. The refrigerant leaves the compressor as a hot, dense vapor and flows through a heat exchanger called the condenser, which transfers heat from the refrigerant to a body of air. Now the refrigerant, as a high-pressure, cooled liquid, confronts a flow restriction which causes the pressure to drop. As the pressure falls, the refrigerant expands and partially vaporizes, becoming chilled. It then passes through a second heat exchanger, the evaporator, which transfers heat from the air to the refrigerant, reducing the temperature of this second body of air. Of the two heat exchangers, one is located inside, and the other one outside the house, so each is in contact with a different body of air: room air and outside air, respectively.

Quote:
Now, if under certain conditions a heat pump puts out more thermal energy than it consumes in electrical energy, has the law of energy conservation been challenged? No, not even remotely: the additional input of thermal energy into the circulating refrigerant via the evaporator accounts for the difference in the energy equation.

The second paragraph , which is fascinating detailed, and the 4th one in which is explained that no contradictory information was given leads us to C. if you keep in mind the big picture and not get lost in those details, i.e. you see the perspective, then C is easy to pick. I did not even read more than two answer choices. C straight

----------------------------------------------------------------------

19. It can be inferred from the passage that, in the course of a heating season, the heating capacity of a heat pump is greatest when

(A) heating is least essential
(B) electricity rates are lowest
(C) its compressor runs the fastest
(E) the heating demand surges

Here, then, lies a genuine drawback of heat pumps: in extremely cold climates-where the most heat is needed-heat pumps are least able to supply enough heat.

A is the answer. Notice how in this question at least a couple of answer choices could be ruled out even without reading the passage. Just for logic or the intention of the passage itself to explain something about heat pumps

----------------------------------------------------------------------

20. If the author's assessment of the use of heat pumps is correct, which of the following best expresses the lesson that advertisers should learn from this case?

(A) Do not make exaggerated claims about the products you are trying to promote.
(C) Do not use facts in your advertising that will strain the prospective client's ability to believe.
(D) Do not assume in your advertising that the prospective clients know even the most elementary scientific principles.
(E) Concentrate your advertising firmly on financially relevant issues such as price discounts and efficiency of operation.

Quote:
The use of heat pumps has been held back largely by skepticism about advertisers' claims that heat pumps can provide as many as two units of thermal energy for each unit of electrical energy used, thus apparently contradicting the principle of energy conservation.

Basically the first passage tells us that heat pumps can achieve some sort of performance even though this would contradict the principle of energy. Now it seems already confused but what it is saying is that IF we go in-depth explanatory of this stuff we get lost. And after all the prospective client's ability is not interested in it. In the end, the customers will not buy a heat pump.

Notice how this question is pretty tricky

(A) Do not make exaggerated claims about the products you are trying to promote.

no advertising campaign or publicity or else surfaces from the passage

Vague analogies. No on point

(C) Do not use facts in your advertising that will strain the prospective client's ability to believe.

Correct

(D) Do not assume in your advertising that the prospective clients know even the most elementary scientific principles.

I do not see anything of knowledge related facts or we do understand something from the client's point of view.

(E) Concentrate your advertising firmly on financially relevant issues such as price discounts and efficiency of operation.

No financial issues emerged.

Regards
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Re: The use of heat pumps has been held back largely by skeptic   [#permalink] 13 Feb 2020, 14:27
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