// Numbas version: finer_feedback_settings
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Superheated refrigerant R134a is used as the coolant during this process, which enters the heat exchanger at 2 bar and {T_in} &deg;C, and exits at 1.8 bar and {T_out} &deg;C.&nbsp;</p>\n<p>You may assume that kinetic and potential energy effects are negligible, no work is done by the heat exchanger, and heat is lost from the heat exchanger to the surroundings at a rate of {Q_dot} kW.</p>", "advice": "", "rulesets": {}, "extensions": [], "builtin_constants": {"e": true, "pi,\u03c0": true, "i": true}, "constants": [], "variables": {"m_dots": {"name": "m_dots", "group": "Ungrouped variables", "definition": "random(0.1 .. 1#0.05)", "description": "<p>Mass flow rate of propane</p>", "templateType": "randrange", "can_override": false}, "v": {"name": "v", "group": "Ungrouped variables", "definition": "random(0.1 .. 0.6#0.01)", "description": "<p>Specific volume of propane</p>", "templateType": "randrange", "can_override": false}, "T_in": {"name": "T_in", "group": "Ungrouped variables", 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"Ungrouped variables", "definition": "561.47 + (x*2163.8)", "description": "<p>Outlet specific enthalpy of propane</p>", "templateType": "anything", "can_override": false}, "h_r1": {"name": "h_r1", "group": "Ungrouped variables", "definition": "258.89 + ((T_in - 10)*((267.78 - 258.89)/(20 - 10)))", "description": "<p>Inlet specific enthalpy of refrigerant</p>", "templateType": "anything", "can_override": false}, "h_r2": {"name": "h_r2", "group": "Ungrouped variables", "definition": "295.45 + ((T_out - 50)*((304.79 - 295.45)/(60 - 50)))", "description": "<p>Outlet specific enthalpy of refrigerant</p>", "templateType": "anything", "can_override": false}, "m_dotr": {"name": "m_dotr", "group": "Ungrouped variables", "definition": "(-((-Q_dot*1000) + m_dots*((h_s1 - h_s2)*1000)))/((h_r1 - h_r2)*1000)", "description": "<p>Mass flow rate of refrigerant</p>", "templateType": "anything", "can_override": false}}, "variablesTest": {"condition": "", "maxRuns": 100}, "ungrouped_variables": ["m_dots", "v", "T_in", "T_out", "Q_dot", "h_s1", "x", "h_s2", "h_r1", "h_r2", "m_dotr"], "variable_groups": [], "functions": {}, "preamble": {"js": "", "css": ""}, "parts": [{"type": "gapfill", "useCustomName": true, "customName": "a)", "marks": 0, "scripts": {}, "customMarkingAlgorithm": "", "extendBaseMarkingAlgorithm": true, "unitTests": [], "showCorrectAnswer": true, "showFeedbackIcon": true, "variableReplacements": [], "variableReplacementStrategy": "originalfirst", "nextParts": [], "suggestGoingBack": false, "adaptiveMarkingPenalty": 0, "exploreObjective": null, "prompt": "<p>Calculate the specific enthalpy of the steam at the inlet and outlet of the heat exchanger:</p>\n<p>$h_{in}$ (kJ/kg) = [[0]] &nbsp;</p>\n<p>$h_{out}$ (kJ/kg) = [[1]] &nbsp;</p>", "gaps": [{"type": "numberentry", "useCustomName": true, "customName": "Inlet Specific Enthalpy of Steam", "marks": 1, "scripts": {}, "customMarkingAlgorithm": "", "extendBaseMarkingAlgorithm": true, "unitTests": [], 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"nextParts": [], "suggestGoingBack": false, "adaptiveMarkingPenalty": 0, "exploreObjective": null, "minValue": "h_s2*0.99", "maxValue": "h_s2*1.01", "correctAnswerFraction": false, "allowFractions": false, "mustBeReduced": false, "mustBeReducedPC": 0, "precisionType": "dp", "precision": "1", "precisionPartialCredit": 0, "precisionMessage": "You have not given your answer to the correct precision.", "strictPrecision": false, "showPrecisionHint": true, "notationStyles": ["plain", "en", "si-en"], "correctAnswerStyle": "plain"}], "sortAnswers": false}, {"type": "gapfill", "useCustomName": true, "customName": "b)", "marks": 0, "scripts": {}, "customMarkingAlgorithm": "", "extendBaseMarkingAlgorithm": true, "unitTests": [], "showCorrectAnswer": true, "showFeedbackIcon": true, "variableReplacements": [], "variableReplacementStrategy": "originalfirst", "nextParts": [], "suggestGoingBack": false, "adaptiveMarkingPenalty": 0, "exploreObjective": null, "prompt": "<p>Calculate the specific enthalpy of the refrigerant as it enters and exits the heat exchanger:</p>\n<p>$h_{in}$ (kJ/kg) = [[0]] &nbsp;</p>\n<p>$h_{out}$ (kJ/kg) = [[1]] &nbsp;</p>", "gaps": [{"type": "numberentry", "useCustomName": true, "customName": "Inlet Specific Enthalpy of Refrigerant", "marks": 1, "scripts": {}, "customMarkingAlgorithm": "", "extendBaseMarkingAlgorithm": true, "unitTests": [], "showCorrectAnswer": true, "showFeedbackIcon": true, "variableReplacements": [], "variableReplacementStrategy": "originalfirst", "nextParts": [], "suggestGoingBack": false, "adaptiveMarkingPenalty": 0, "exploreObjective": null, "minValue": "h_r1*0.99", "maxValue": "h_r1*1.01", "correctAnswerFraction": false, "allowFractions": false, "mustBeReduced": false, "mustBeReducedPC": 0, "precisionType": "dp", "precision": "1", "precisionPartialCredit": 0, "precisionMessage": "You have not given your answer to the correct precision.", "strictPrecision": false, "showPrecisionHint": true, "notationStyles": ["plain", "en", 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"c)", "marks": "2", "scripts": {}, "customMarkingAlgorithm": "", "extendBaseMarkingAlgorithm": true, "unitTests": [], "showCorrectAnswer": true, "showFeedbackIcon": true, "variableReplacements": [{"variable": "h_s1", "part": "p0g0", "must_go_first": true}, {"variable": "h_s2", "part": "p0g1", "must_go_first": true}, {"variable": "h_r1", "part": "p1g0", "must_go_first": true}, {"variable": "h_r2", "part": "p1g1", "must_go_first": true}], "variableReplacementStrategy": "originalfirst", "nextParts": [], "suggestGoingBack": false, "adaptiveMarkingPenalty": 0, "exploreObjective": null, "prompt": "<p>Calculate the mass flow of R134a required in kg/s.</p>", "minValue": "m_dotr*0.99", "maxValue": "m_dotr*1.01", "correctAnswerFraction": false, "allowFractions": false, "mustBeReduced": false, "mustBeReducedPC": 0, "precisionType": "dp", "precision": "3", "precisionPartialCredit": 0, "precisionMessage": "You have not given your answer to the correct precision.", "strictPrecision": false, 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